Neuroanatomy & Neurochemistry: Overview of Neurons, Neuroglia, & Hormonal Interactions, Summaries of Anatomy

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E. Odya,

Anatomy and

physiology

BSCI 201 Final Exam Study Guide Monday, December 17th, 8 AM- 10 AM in our normal classroom, BRB 1101 Good luck tomorrow everyone! :) Format:

● 40 multiple-choice questions (2 points each) from mostly the Nervous system - you will put your

answer on scantron (bring pencils) (80 points)

● 40 True/false statement (2 points each) from all information covered - you will put your answer

on scantron (A for True; B for False) (80 points)

● 10 short answer/free response(50 points)

● 15 Matching statements (correct letters will form a sentence, as usual) (30 points)

● Total will be out of 220 points + 20 possible extra credit = up to 240 points can be earned

The Nervous System

1. Why are neurons amitotic? a. Neurons contain a nucleus and all other cytoplasmic organelles EXCEPT centrioles, which are needed for cells to divide. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell. Do primary brain tumors originate from neurons in the brain or the supporting cells (neuroglial cells)? Explain your answer b. Neuroglial cells - neurons are amitotic, they do not have centrioles needed to divide, hence cannot replicate/proliferate; only supporting cells are capable of doing this, because they have the capability to proliferate uncontrollably. The other way to have a brain tumor would then be through metastasis of cancer from another part of the body but this would be a secondary brain tumor.
2. Which part of a neuron is known as the: a. biosynthetic center and why? i. Cell body- all biosynthetic activities occur in the cell body b. receptive center and why? i. Dendrites - receive and convey electrical signals towards cell body c. conducting region and why? i. Axon-generates and transmits action potentials away from cell body d. How many axons can each neuron have? i. Only ONE e. secretory region and why? i. Axon terminals - release neurotransmitters into extracellular space
3. Define the following a. Nissl body- well developed rough ER, involved in metabolic activity and oxygen supply for neurons b. Ganglion- cluster of neuron cell bodies in PNS c. Nucleus- cluster of neuron cell bodies in the CNS d. Tract- bundle of axons in CNS e. Nerve- bundle of axons in PNS f. Neurilemma- outermost nucleated cytoplasmic layer of schwann cells that surrounds the axon of neurons in the PNS g. Nodes of Ranvier- spaces between adjacent myelin sheaths (covering each Schwann cell) that facilitate rapid electric conduction. h. Endoneurium- connective tissue that covers each axon

i. Na+^ influx ii. - 70 to +30mv c. repolarization phase of an action potential- i. after AP, K+^ efflux ii. +30 to - 70mv d. hyperpolarization phase- i. more K+^ efflux, ii. - 70 to - 90mv iii. then return to RMP of - 70mv

10. What are the absolute refractory period and relative refractory period of an action potential? a. Absolute Refractory Period: Occurs when the sodium gates are still open (depolarization phase) and the neuron is unable to initiate a new action potential b. Relative Refractory Period: When the neuron is undergoing repolarization and therefore the sodium gates are closed, an exceptionally strong stimulus can cause initiation of another action potential
11. How do you tell the difference between a strong stimulus (such as an intense pain) and a weak stimulus (such as a mild pain) that caused action potential generation? a. If there are more frequent action potentials (more waves on the graph) that indicates a strong stimulus. If there are less frequent action potentials (less/fewer waves on the graph) then that indicates a weaker stimulus.
12. Name and describe the 3 structural classes of neurons- a. Uni/pseudopolar- A single process extending from the cell body- divided into peripheral and central processes (conduct impulses toward the CNS) Bipolar- Two processes attached to the cell body- one dendrite, one axon (found only in the eye, ear, and olfactory mucosa) Multipolar- Many processes issued from the cell body- many dendrites, one axon (most abundant type of neurons in the body) b. which structural class is most abundant? i. multipolar
13. Name and describe the 3 functional classes of neurons a. Sensory (afferent) Neurons- Carry impulses from sensory receptors in skin, internal

organs, muscles and special sense organs toward the CNS Motor (efferent) Neurons- Carry impulses away from the CNS to organs, muscles, and glands Association Neurons (Interneurons)- Conduct impulses within the CNS b. which functional class is most abundant? i. association/interneurons (99% in the human body)

14. Name and describe the 3 types of nerve fibers. a. Group A: Have largest diameter and heavily myelinated; transmits impulses at a rate of 150 m/s (Ex. Motor Neuron) b. Group B: Intermediate Diameter and lightly myelinated, transmits impulses at a rate of 15 m/s c. Group C fibers: Smallest diameter and unmyelinated; transmits at a rate of 1 m/s d. Which type has the fastest conduction velocity and why? i. A fibers, largest diameter, myelinated, fastest, lowest resistance e. Which type has the slowest conduction velocity and why? i. C fibers, smallest diameter, unmyelinated, highest resistance. slowest. f. Explain what happens to the conduction velocity when myelinated axons become demyelinated. i. The conduction velocity decreases bc myelin insulate the axonal membrane, reducing the ability of current to leak out of the axon and thus increasing the distance along the axon that a given local current can flow passively. (also due to lack of ability to jump, needs travel farther which means slower) CNS: Brain
15. Name the 4 structures protecting the brain. Cranium, Meninges, CSF (cerebral spinal fluid), and blood brain barrier (BBB) a. What is the significance of the Blood Brain Barrier? Protects the brain and nerves, nerve cells from contact with the blood. Also serves as additional shock absorption and insulation within/around cranial structure. Also provides nutrients and O 2 to brain.
16. Name and describe the 3 types of meninges. Which meninx is double-layered? Outermost meninge called dura mater which is double layered (tough and inflexible, forms structures that separate the cranial cavity into compartments), middle arachnoid mater, and the inner pia mater. The other two aids in the transfer/production of CSF. a. CSF is located in one area outside the brain and four areas inside the brain – name these areas. i. the subarachnoid space outside of the brain and spinal cord , the two lateral ventricles, the third ventricle, and the fourth ventricle. b. Give the locations of the lateral, third and fourth ventricles. Two lateral in cerebral cortex (span cerebrum, including occipital, frontal and parietal lobes), continued by the 3rd in the diencephalon of the forebrain between the right and left thalamus, and the fourth is located at the back of the pons and upper half of the medulla oblongata of the hindbrain. The ventricles aid in the production/circulation of the cerebrospinal fluid. a. Give the location of the interventricular foramen and cerebral aqueduct i. The interventricular foramen connects the paired lateral ventricles with the third ventricle at the midline of the brain ii. The cerebral aqueduct is within the midbrain and contains the cerebrospinal fluid. It also

(motor strip). It controls the voluntary movements of skeletal muscles. Additionally, cell bodies of the pyramidal tract are on this gyrus.

7. Discuss the contralateral control of voluntary skeletal muscle movements by the cerebral cortex. a. Opposite side brain/cerebrum and brainstem/spinal cord, opposite side brain/cerebrum and limbs. Same side brainstem, spinal cord and limbs(continuous). b. Pyramidal tract from cell bodies of right precentral gyrus cross to left side and innervate muscles on left side c. The precentral gyrus houses pyramidal cells that are called pyramidal tracts when they are bundled up. They descend to the lower brain and decussate (cross over) when they get to the spinal cord. Contralateral control is what happens when pyramidal tracts from cell bodies in the RIGHT precentral gyrus cross over to the LEFT side, to innervate skeletal muscles on the LEFT SIDE OF THE BODY.
8. What is the consequence of: a. damage to the precentral gyrus in the left cerebral hemisphere Degeneration of left pyramidal tract, loss of voluntary skeletal muscle movements on right side = right side paralysis b. damage to the postcentral gyrus in the right cerebral hemisphere loss of sensation in the left side of the body c. damage to the Broca’s area is destroyed- inability to speak
9. What is Broca’s aphasia? What is Wernicke’s aphasia? a. wernicke’s is “word salad” and random, nonsensical, incoherent sound or speech. b. Broca’s is inability to speak or communicate verbally what one thinks or wants to say. c. The two regions are joined by the arcuate fasciculus, but are different, and in different regions of brain (broca’s frontal lobe, and wernicke’s temporal lobe) even though both related to speech function. d. Explain why right side paralysis may be accompanied by Broca’s aphasia. i. broca’s area is only in the left frontal lobe of the cerebral hemisphere, and right side paralysis has to do with left side cerebral brain damage. And right side brainstem/spinal cord damage. “Contralateral control” e. Will left side paralysis accompanied by Broca’s aphasia? i. NO, Broca’s only on left frontal lobe on brain, but if the left frontal lobe damaged as well, it will include broca’s. Broca’s area is ABSENT on right frontal lobe
10. What is the consequence of damage to the right postcentral gyrus? a. Somatosensory damage (homunculus). Left side loss of sensation
11. Name the 3 main cerebral basal nuclei; discuss their function. Caudate nucleus-motor and behavioral functions Putamen-motor function and physical movement, skeletal muscle innervation Globus pallidus-voluntary movement regulation
12. What is the pathogenesis of Parkinson’s disease? a. Damage to the dopaminergic neurons b. Explain why L-DOPA is used to manage Parkinson’s disease; explain why dopamine is not used: i. L-Dopa is nonpolar and a precursor to dopamine. L-Dopa can cross the blood brain barrier, where it will reach the basal nuclei in the cerebrum, diffuse, and be converted into dopamine. Dopamine is not used first because it is polar and can’t cross the blood brain barrier Diencephalon
13. Which area in the diencephalon is referred to as the “Gateway to the cerebral cortex” and why?

a. THALAMUS- all sensory input must stop in thalamus before projecting to respective cerebral cortex

2. Name two areas in the diencephalon with endocrine function a. Epithalamus and hypothalamus Brainstem
3. Structurally, how is the brainstem similar to the spinal cord a. brain stem continuous with spinal cord b. both contain tracts (bundles of nerves)
4. name the 3 parts of the brainstem a. composed of the midbrain, pons, and medulla oblongata
5. What are the corpora quadrigemina and what are their functions? a. superior colliculus-visual reflex center b. inferior colliculus-auditory reflex center
6. Name and give the function of the 2 pigmented nuclei in the midbrain a. red nuclei- control limb flexion b. Substantia nigra- send dopaminergic neurons to basal nuclei to control function of basal nuclei (initiation/halting of voluntary skeletal muscles)
7. How many of the cranial nerves have their cell bodies located in the brain stem? 10 of the 12 cranial nerves (CN3-CN12) (all except olfactory and optic nerves) Explain why trauma to the brain stem can be fatal. a. Damage to brainstem means no signals to or from brain b. no function of the thalamus and involuntary organs(heart,lungs,hormones), means death
8. Where does the decussation of the pyramids occur and what is the consequence of this decussation? a. Affects contralateral control (opposite side cerebral brain parts and body). The two medullary pyramids contain motor fibers that go from the brain to the medulla oblongata and spinal cord (the corticobulbar/spinal fibers that make up pyramidal tracts), they decussate (cross over) in the anterior fissure of the medulla oblongata Cerebellum
9. In the cerebellum what is the “Arbor Vitae? a. network of white matter within the gray matter
10. What is the vermis? a. holds cerebellar hemispheres together medially
11. Name the cerebellar lobe that cannot be viewed on the surface of the cerebellar hemispheres a. Flocculonodular lobe
12. The tandem walk test involves walking in a straight line with one foot immediately in front of the other (heel to toe) – the inability to maintain balance during a tandem walk due to alcohol intoxication is indicative of impairment of which brain region? a. Cerebellum coordinates/balance skeletal muscle movements, alcohol affects function hence failed tandem walk CNS: Spinal Cord
13. Describe the arrangement of the gray matter and the white matter (compare this arrangement to the brain stem; compare to the cerebrum and cerebellum) Cerebellum and cerebrum- inner white matter, outer gray matter Brainstem and spinal cord- inner gray matter, outer white matter
14. Define a. spinal dural sheath-Single layered dura mater. Has an existing space between internal surface of

Sensory Organs The eye

1. Name the 3 major parts of the eye Tri-layered eye wall, humors (fluids), and the lens a. what is the function of the lens in the eye? i. Reflect and refract light from cornea at the front of the eyeball to the photoreceptors at the back of the eyeball (with the retina)
2. Name and describe the 3 layers of the wall of the eye. a. Fibrous outer layer: Avascular dense regular CT. b. Vascular middle layer (3 parts): Anterior iris, middle ciliary body, and posterior choroid c. Sensory inner layer: Confined to back of eye → fundus. Avascular so pigmented layer receives nutrients from choroid d. What structure forms the most anterior part of the eye? i. cornea
3. Give the location and function of the a. Sclera-back whites of eyes posterior ⅚ of eye b. Cornea-front clear of eyes anterior ⅙ of eye c. Pupil-center of eye, allows light to enter eye d. Rods-black and white vision, dim light e. Cones-color vision, bright light, red, green, and blue cones(trichromatic theory) f. Suspensory ligament-holds lens in place g. Optic disc-where the optic nerve runs from back of eyeball. Also called blindspot. No rods or cones h. Macula lutea- used for hard focus i. fovea centralis.- contains ONLY cones, at center of macula lutea and has highest visual acuity
4. Which structure is known as the “white” of the eye? sclera b) Name the visible colored part of the eye iris
5. Name and discuss the two humors in the eye.

Aqueous and vitreous (front and middle) b) Discuss the functions of each humor. Aqueous humor: Filtered to anterior part of lens to provide nutrients to avascular cornea/lens. Vitreous humor: Posterior part of lens to support the lens & compress neural layer against pigmented layer c) Which humor in the eye is formed and drained throughout life? AQUEOUS d) Which humor is formed during embryonic development and stays for a lifetime? VITREOUS e) What is the function of the canal of Schlemm? Drains the aqueous humor regularly via veins, etc. f) What is glaucoma? Can cause blindness when lens/photoreceptors are destroyed. This condition (glaucoma) can be caused when the canal of schlemm is blocked, due to increase in filtration rate and decrease in drainage if there is an increase of the aqueous humor.

6. The sensory layer is double-layered – name the two layers. Outer pigmented layer and inner neural layer b) Discuss the functions of the cells in the pigmented layer. Located at the rear of the retina, this layer contains pigmented epithelial cells that absorb light and prevents light rays that were not absorbed by the neural layer from scattering. By preventing reflection of light within the eye, the pigmented layer helps make sure that the only light getting to rods and cones comes through the lens as a focused image. c) The neural layer, also known as the retina, consists of 3 layers of neurons – name these neurons. Photoreceptors → bipolar neurons → ganglion d) Name the two types of photoreceptors – which type is more sensitive to light? Rods - dim light, not good for color vision, sensitive to light Cones- bright light, color vision
7. What happens when the right optic nerve is severed? Right side blindness What happens when the right optic tract is severed? loss of sight in the left visual field What happens when the right primary visual cortex in the right occipital lobe is damaged? Both eyes partial blindness (controls both eyes) f) What is retinal detachment? Explain how retinal detachment can lead to blindness. When retina separates from blood vessels of the eyeball. Causes blurry vision, incorrect visual signals, extremely dangerous. The continuous loss of sight will eventually lead to blindness.
8. Give the location and function of the (a) Lateral geniculate nucleus/LGN-thalamus, visual relay center in brain. (b) superior colliculi-upper part of the corpora quadrigemina, for visual reflex control center (c) primary visual cortex- Occipital lobe, controls sight ability
9. Trace the pathway of light through the eye from the cornea to the photoreceptors Cornea→ aqueous humor → pupil → lens → vitreous humor→ retina→ photoreceptors → optic nerve → occipital lobe The axons of which type of neurons in the retina form the optic nerve and generate/ transmit action potentials? Ganglion cells
10. Describe the path taken by light through the neural layer; describe the path taken by electrical signals

b) cristae ampullares- in the anterior, posterior and lateral semicircular canals within inside/labyrinth of ear

6. Describe the organ of Corti; give the location The organ of corti is the receptor organ for hearing in the cochlea. Its strip of epithelial cells allows transduction of auditory signals into nerve impulses’ action potential. This transduction occurs through vibrations of inner ear structures, displacing cochlear fluid and creating movement of hair at this organ. (a) Basilar membrane - 1st outer layer (b) Supporting cells- Hair cells trapped in the tectorial membrane (d) Tectorial membrane-2nd inner layer Name the mechanoreceptors for hearing Hair cells
7. Trace the path taken by sound waves through the ear. What determines a) Loudness? Basilar membrane b) Pitch? Cochlear stereocilia
8. Give the location and function of a) medial geniculate nucleus- in thalamus, auditory relay center b) inferior colliculus.-in lower part of corpora quadrigemina, auditory reflex control center c) Primary auditory cortex- temporal lobe; hearing d) What happens when the left primary auditory cortex is damaged? deafness or partial deafness in left ear Olfaction (Sense of Smell)
9. What type of cells are the olfactory cells and why are they considered unique in humans? Epithelial cells; exhibit longevity
10. What are the two criteria a chemical must meet for olfactory processing to occur?
    1. Must dissolve in thin layer of mucus
    2. Must be volatile (gaseous)
11. Axons of which neurons form (a) olfactory nerve? Olfactory neurons (b) olfactory tract? Mitral neurons/cells Gustation (Sense of Taste)
12. Name the three types of cells in a taste bud? Basal cells, supporting cells, gustatory cells. a. What type of cells are the gustatory cells? i. Taste bud receptor cells
13. Name the 3 cranial nerves that carry taste information facial (CN VII), glossopharyngeal(CN IX) and vagus(CN X); Name the gustatory relay center in the thalamus. Ventral posterior medial (VPM) nucleus, then to INSULA.

3. In which cerebral lobe is the primary gustatory cortex located? Insula The Endocrine System
4. What is the difference between a hormone and a neurotransmitter? ● A hormone is a chemical that is secreted by specialized glands called endocrine glands into the bloodstream (important for digestion, metabolism, growth, reproduction). ● A neurotransmitter is a chemical released from a nerve cell which transmits an impulse from a nerve cell to another nerve/muscle/organ/tissue over a synapse.
5. Define negative feedback mechanism as it pertains to hormonal actions

• A hormone released in response to a stimulus (homeostatic imbalance) works via NEGATIVE FEEDBACK mechanism to maintain homeostasis.
• Negative Feedback Mechanism – the biological effects of hormones negate/eliminate/obliterate the stimuli that caused the release of the hormones a. Ex: a high level of a particular hormone in the blood can inhibit further secretion of that hormone. Cortisol binds to its receptor on cells in the hypothalamus and inhibits hormones such as CRH and ACTH. The less these hormones are released the less cortisol is secreted and vice versa.

3. Name and discuss the 3 chemical classes of hormones; which class is derived from the amino acid tyrosine? Which class is derived from cholesterol? ● Biogenic amine hormones – hormones derived from the amino acid TYROSINE; such as dopamine, catecholamines ○ Biogenic hormones are generally polar chemicals ○ Bind to membrane receptors ● Peptide/protein/glycoproteins hormones - hormones composed of a sequence of amino acids: attain structural complexity; protein with carbohydrate moiety attached; such as oxytocin, insulin, follicle stimulating hormone ○ These hormones are polar chemical ○ Bind to membrane receptors ● Steroid hormones – hormones derived from cholesterol; such as testosterone ○ Steroid hormones are non polar chemicals ○ Think of cholesterol like oil, which is nonpolar because it does not mix with polar water. ○ Bind to intracellular receptors
4. What are target cells for a hormone? Anything that responds because it has the receptors for that specific hormone(ligand), cannot be affected by anything else or allow to bind unless has those specific receptors
5. Discuss the characteristics of hormone receptors. There are two types of hormone receptors – membrane receptors and intracellular receptors: discuss which class/classes of hormones bind/s to each type of receptors. Hormone receptors are specific. Membrane receptors are on the plasma membrane surface, which usually imply ligands binding to them and being released; biogenic amine and peptide hormones Intracellular receptors are within the cytoplasm, and usually transport hormones to/from/through the membrane; steroid hormones
6. Name and discuss the 4 types of hormone INTERACTIONS with receptors. Hormonal Interactions – describe how hormones interact with their receptors on/in target cells

• Classical Endocrine Interaction – endocrine gland releases a hormone into the bloodstream which transports the hormone to its target cells.
• Paracrine Interaction – endocrine cells release hormone into interstitial fluid surrounding the neighboring target cells. Typically, the endocrine cells and the target cells are “neighbors” –

E. Discuss two cytoplasmic organelles that will be prominent in a metabolically-active cell.

1. Mitochondria (ATP synthesis)
2. golgi (ribosomes, protein, etc) F. Discuss three structures that will be prominent in a phagocyte.
3. Lysosomes
4. rough ER
5. golgi body G. Which cytoplasmic organelle will be prominent in steroidogenic cells? Smooth ER H. Which cytoplasmic organelle is involved in drug detoxification Smooth ER i) Describe the phases of a CELL’S LIFE CYCLE
6. G1(interphase) a. Cell grows in size, copies organelles
7. Synthesis (interphase) a. Copies DNA and centrosomes
8. G2 (interphase) a. Cell grows more and prepares for mitosis by creating proteins and organelles
9. Mitosis a. Prophase- chromosomes are condensed and become compact (heterochromatin), mitotic spindle forms, nucleolus breaks down i. Prometaphase- membrane vesicles formed, chromatids formed, kinetochores formed around centromere b. Metaphase- chromosomes line up in middle of cell, each kinetochore is attached to a microtubule from an opposite spindle poll c. Anaphase- chromosomes are pulled apart d. Telophase- mitotic spindle breaks, two new nuclei form, chromosomes decondense (euchromatin) e. Cytokinesis- in animals, cleavage furrow pinches cells apart. In plants, cell plate splits cells with two new cell walls
10. G0 phase- cell is not preparing for replication, it is simply carrying out its duties Discuss four ways you will design effective chemotherapeutic drugs based on the life cycle of cells.
11. Prevent division/cell number
12. prevent spindle fibers splitting
13. prevent DNA replication
14. prevent cell growth size j) Define: Hypertrophy- growth in size (think, trophies are tall) Hyperplasia- growth in number (think, you own a large number of plastic containers) From Exam 2 a) Discuss the thermoregulatory function of the Integumentary system a. Sweat cools down the skin and also protects your body from microbial growth.

b. When sweat is released hypotonic fluid is evaporated using heat from the body. c. Additionally, arrector pili muscles of hair trap air to retain heat by changing in orientation to a 90 degree angle in order to trap a layer of heat on your skin and keep the body warm b) Discuss the physical and chemical protections of the integumentary system Acid mantle- it is made of oils, sweat, dermcidin (antimicrobial protein) and dead skin released from the dermis and creates a layer of acidic solution when mixed with the epidermis. It is slightly more acidic in nature preventing harmful substances from getting into the skin. The low pH (4.6-5.5) prevents microbial infection. Another way the integumentary system protects the skin is through melanin which is generated through exposure to UV radiation, it is an absorbent of light and can dissolve the majority of absorbed UV radiation. c) Define “epiphyseal plate closure” – how does it occur? What is the consequence of epiphyseal plate closure? Gonadal steroids such as estrogen and testosterone can cause the closure of the epiphyseal growth plates in late adolescence. The cartilage then becomes replaced with bone and statural growth ceases. The epiphyseal line is formed after child stops growing. Consequence- if it closes too early, could cause someone to too short, or if it closes too late, can cause someone to be unnaturally tall (?) d) State Wolff’s Law. Discuss three examples where this law is applicable or supported.

1. Bones grow throughout life and every time stress or tension is applied to them they remodel and regenerate in order to adapt. Bones become thicker/stronger over time to resist forces placed on them and thinner/weaker if there are not forces to act against. a. Spending a lot of time in space, no pull on gravity, bone density loss. b. Being bedridden results in a loss of bone density. c. Weightlifters have an increase in bone density with continuous training d. The bones in a tennis player’s dominant arm can be thicker in density than the bones in the non-dominant arm. e) Name and describe the type of synovial joint that allows us to motion “no” Atlanto-axial joint. Pivot joint with uniaxial rotation around an axis, involves a cylinder bony process that rotates in a circle of bone (and ligament). Name and describe the type of synovial joint that allows us to motion “yes” Atlanto-occipital joint. Condyloid joint where one bone is shaped like a cup and the other fits into it with a rounded flask-like shape. Describe a saddle joint. Indicate one location in the body where a saddle joint is found. A synovial joint formed between bones whose articulating surfaces have both concave and convex regions, complementary to each other. This allows for greater freedom of movement. An example would be the carpometacarpal joints of the thumb. From Exam 3
2. Discuss the role of ATP in muscle contraction. ● ATP is hydrolyzed by ATPase to produce ADP and Pi to activate myosin globular heads and for crossbridge detachment (explained below) ● ATP is also used for the sequestration of calcium ions back in to SR for storage
3. ATP binds to myosin and is hydrolyzed into ADP + Pi by ATPase
4. Energy released changes the angle of the myosin head into a position that allows it to bind to actin
5. As Ca2+^ ions bind to troponin, exposing active-binding sites on the actin and letting myosin head bridge the gap, a cross-bridge is formed

skeletal muscle contraction? Block Ca2+^ entry into smooth/cardiac muscle cells, which will inhibit smooth/cardiac muscle contraction. The calcium channel blockers have no effect on skeletal muscle contractions.

6. How does acetylcholinesterase inhibitor affect skeletal muscle contraction? Acetylcholinesterase will destroy acetylcholine in the neuromuscular cleft, halting motor neurons activation, and in effect, prevent skeletal muscle contraction.