A&P exam study guide

Describe the functions of prime movers, antagonists, and synergists.

Prime movers: Responsible for producing specific movement (pushing, pulling)

Antagonist: opposes or reverses particular movements (works against prime movers)

Synergist: adds extra force to same movement (works with prime movers)

Explain how a muscle’s position relative to a joint affects its action.

• A muscle that crosses on the anterior side of a joint produces FLEXION

• A muscle that crosses on the posterior side of a joint produces EXTENSION

• A muscle that crosses on the lateral side of a joint produces ABDUCTION

• A muscle that crosses that medial side of a joint produces ADDUCTION

List the criteria used in naming muscles. Provide an example to illustrate the use of each criterion.

• Muscle Location: bone/body region

• Muscle Shape: distinctive shapes

• Muscle Size: maximus, minimus, longus

• Direction of muscle fibers: rectus, transversus, oblique

• Number of origins: like bicep as 2 origins and triceps have 3 

• Location of attachment: where the point of origin and insertion is

• Muscle action: what action is produces

Define lever, and explain how a lever operating at a mechanical advantage differs from one operating at a mechanical disadvantage.

Lever: a rigid bar that moves on a fixed point called the fulcrum (joint) when force is applied to it.

Mechanical advantage: load is close to fulcrum; effort is far from fulcrum

Mechanical disadvantage: load is far from fulcrum; effort is close to fulcrum

Name the three types of lever systems and indicate the arrangement of effort, fulcrum, and load in each. Also note the advantages of each type of lever system.

First class: Fulcrum is between load and effort

(seesaw scissors)

Second class: Load is between fulcrum and effort (standing on toes)

Third class: Effort is between load and fulcrum (tweezers) (skeletal muscles)

List the basic functions of the nervous system.

• sensory input

• integration

• motor output

Explain the structural and functional divisions of the nervous system.

• central nervous system: brain and spinal cord; control center of the nervous system

• peripheral nervous system: part of the nervous system outside the CNS, consists of nerves (broken down into the sensory and motor division)

List the types of neuroglia and cite their functions.

• astrocytes: supports and braces the neurons and anchors them to their nutrient supply lines

• microglial cells: touches nearby neurons, monitoring their health and when they sense that certain neurons are injured or in other trouble, they migrate towards them

• ependymal cells: beating of their cilia helps to circulate the cerebrospinal fluid which cushions the brain and spinal cord

• oligodendrocytes: lines up along the thicker nerve fibers in the CNS and wraps their processes around the fibers creating the myelin sheath

Define neuron, describe its important structural components, and relate each to a functional role.

neuron: structural units of the nervous system

• body: part of receptive region; biosynthetic canter of neuron

• axon: slender process extending from neuron; conducting region; generates nerve impulses and transmits them

• dendrites: main receptive or input regions

Differentiate between (1) a nucleus and a ganglion, and (2) a nerve and a tract.

1. a nucleus is a cluster of neuron cell bodies found only in the CNS and a ganglion is a name for cluster of neuron cell bodies found only in the PNS.

2. a nerve is one or more bundles of nerve fibers(axons in the PNS and tracts are another name for a nerve, except this bundle of nerve fibers (axons) is only found in the CNS.

Explain the importance of the myelin sheath and describe how it is formed in the central and peripheral nervous systems.

myelin sheath protects and electrically insulates fibers and it increases the transmission speed of nerve impulses

• PNS: formed by Schwann Cells

• CNS: formed by oligodendrocytes

Classify neurons by structure and by function.

structure: multipolar neurons (three or more processes), bipolar neurons (two processes), and unipolar neurons (single short process)
function: sensory neurons (transmit impulses toward or into the CNS), motor neurons (transmit impulses away from the CNS), and interneurons (lie between motor and sensory neurons shuttling signals through CNS pathways)

Describe the relationship between current, voltage, and resistance.

• Ohm’s law

  • Current (I) = Voltage (V) / Resistance (R)

• Current is directly proportional to voltage

(greater the voltage, greater the current)

• Current is inversely proportional to resistance (greater the resistance, the smaller the current)

Identify different types of membrane ion channels.

• Leakage channels (non gated): always open

• Gated channels

  • chemically: opens with binding of a specific chemical

  • voltage: opens and closes in response to changed in membrane potential

  • mechanically: opens and closes in response to physical deformation of receptors as in sensory receptors

Define resting membrane potential and describe its electrochemical basis.

resting membrane potential: the electrical charge difference (typically -70mV to -90mV) across a neuron's membrane when not transmitting signals, with the inside negative relative to the outside

electrochemical basis: the direction that an ion moves

• concentration gradient: moves down chemical concentration gradients from and area of their higher concentration gradients to an area of lower concentration

• electrical gradient: moves towards an area of opposite electrical charge

Describe graded potentials and name several examples.

short-lived localized changes in membrane potential (the stronger the stimulus, the more voltage changed and farther current flows

• postsynaptic potentials (stimulus is released by another neuron

• end-plate potential (occurs in muscle cells (contraction))

• receptor potential (sensory receptor is excited by its stimulus aka light, pressure etc.)

Compare and contrast graded potentials and action potentials.

graded potentials:

• once gated ion channel opens, depolarization spreads (decays quickly)

• acts as signals over short distances

• initiates action potentials

action potentials:

• reversal of membrane potential with voltage change

• signals over long distances

• does not decay over distance

Explain how action potentials are generated and propagated along neurons.

• resting state: channels closed, no movement, flat

• depolarization: Na⁺ channels open, Na⁺ flows into cell

• repolarization: Na⁺ inactivating K⁺ channels open, K⁺ flows out of cell

• hyperpolarization: some K⁺ channels stay open, Na⁺ channels reset (activation gates close; inactivation gates open), some K⁺ continues to flow out

Define absolute and relative refractory periods.

absolute: time from opening of Na⁺ channels until resetting of those channels

• ensures that each AP is all-or-none

• enforces one-way transmission of APs

Relative: follows absolute refractory period

• Most Na⁺ channels return to their resting state some K⁺ channels still open

• threshold for AP generation is elevated

• only exceptionally strong stimulus can trigger another AP

Define saltatory conduction and explain how it differs from conduction in nonmyelinated axons.

Saltatory conduction: fast conduction (30x); occurs only in myelinated axons where as nonmyelinated is a slower (continuous) conduction is non myelinated axons

Define synapse and describe the events that occur at a synapse.

a junction between two neurons where information is transferred

• presynaptic neuron: neuron conducting impulses toward synapse (sends info)

• postsynaptic neuron: neuron transmitting electrical signals away from synapse (receives info)

Distinguish between electrical and chemical synapses by structure and by the way they transmit information.

electrical: less common, electrically coupled

• joined by gap connections

• communications rapid

• found in some brain regions responsible for eye movements, or hippocampus areas for emotion and memory

chemical: most common

• specialized for release and reception of chem messengers neurotransmitters

• composed of two parts separated by synaptic fluid (axon terminal of presynaptic neurons with synaptic vessels) and (receptor region on post synaptic neurons membrane which receives neurotransmitters

Distinguish between excitatory and inhibitory postsynaptic potentials.

excitatory: neurotransmitter binding opens chemically gated channels allowing simultaneous flow of Na⁺ and K⁺ in opposite directions

• Na⁺ influx greater than K⁺ efflux, resulting in local net graded potential depolarization

inhibitory: neurotransmitter binding to receptor opens chemically gated channels that allow entrance/exit of ions that cause hyperpolarization

• If K⁺ channels open, it moved out of cell, if Cl^- channels open, it moved into cell

• reduces postsynaptic neuron’s ability to produce an action potential

Describe how synaptic events are integrated and modified.

• Summation by the post synaptic neuron: temporal (rapid fire impulses) and Spatial (stimulated by large numbers of terminals simultaneously)

• most neurons receive both excitatory and inhibitory inputs from thousands of other neurons

Define neurotransmitter and classify neurotransmitters by chemical structure and by function.

they are the language of the nervous system and is usually released at different stimulation frequencies; classified chemically and functionally

• Acetylcholine (ACh): released at neuromuscular junctions and synthesized from acetic acid and choline

• Catecholamines and Indolamines (biogenetic amines): plays roles in emotional behaviors and biological clock

• Amino acids: make up proteins (glutamate, aspartate, glycine, gamma)

• Peptides: Substance P (mediator of pain signals), Endorphins (natural opiates, reduce pain perception), Gut-brain peptides ( plays tole in regulating digestion)

• Purines: monomers of nucleic acids have an effect in CNS and PNS (ATP for energy and Adenosine for brain inhibitor)

• Gases and lipids (NO and CO gases. binds with G-protein receptors in the brain, NO involved with learning and formation of new memories)

• Endocannabinoids: acts at same receptors as THC, most common g protein, involved in learning and memory and maybe neuronal development, appetite control and suppressing nausea

Describe the action of neurotransmitters at channel linked and G protein–coupled receptors.

channel linked:

• ligand-gated ion channels

• action is immediate and brief

• opens a channel and allows ions to pass through

G protein-linked:

• responses are indirect, complex, slow and often prolonged

• involves transmembrane protein complexes

• cause widespread metabolic changes

Describe the structure and function of accessory eye structures, eye layers, the lens, and humors of the eye.

• Three layers (lens, humors and accessory structures); small sphere, mostly protected by fat cushion and bony orbit

• accessories:

  • eyelids: protects the eye from foreign objects

  • eyebrows: shades eye from sunlight and prevents perspiration

  • eyelashes: lubricates glands

  • conjunctiva: produces lubricating mucous secretion

  • lacrimal apparatus: consists of lacrimal gland and ducts that drain into nasal cavity

  • extrinsic eye muscles: six strap like, four rectus muscles and two oblique muscles

Outline the causes and consequences of cataracts and glaucoma.

cataracts: clouding of the lens (lens thickening) that causes the world to appear distorted. causes by heavy smoking, frequent exposure to intense sunlight and steroid use.

glaucoma: drainage of aqueous humor is backed up, increasing pressure within the eye which compresses the retina and optic nerve. can result in blindness unless the condition is treated early. Usually don’t realize you have it until its too late

Describe the events that convert light into a neural signal.

phototransduction

• visual pigment activates transduction

• transduction activates phosphodiesterase (PDE)

• PDE converts cGMP into GMP

• as cGMP levels fall, cGMP-gated cation channels close causing hyper polarization

Compare and contrast the roles of rods and cones in vision.

rods: dim light, peripheral vision receptors, more numerous and sensitive to light, no color visions or sharp images, numbers greatest at periphery

cones: vision receptors for bright light, high resolution color vision

Compare and contrast light and dark adaptation.

light adaption: both rods and cones are strongly stimulated, large amounts of pigment are broken down instantaneously (causes a glare), pupils constrict

dark adaption: cones stop functioning in low-intensity light, bright lights bleach rod pigments so they’re turned off, pupils dilate

Describe the structure and general function of the outer, middle, and internal ears.

outer: hearing only (external ear)

• auricle (pinna)

• external acoustic meatus)

• tympanic membrane (connects to the middle)

middle: hearing only (tympanic membrane)

• small air-filled, mucosa lined cavity

• pharyngotympanic tube

• Auditory ossicles (malleus, incus, stapes)

internal: hearing and equilibrium

• temporal bone behind eye socket

• bone and membranous labyrinth

• vestibule (saccule and utricle)

• semicircular canals

• cochlea

Describe the sound conduction pathway to the fluids of the internal ear.

1. sound waves vibrate the tympanic membrane
2. auditory ossicles vibrate. pressure is amplified
3. pressure waves create by the stapes pushing on the oval window move through fluid in the scala vestibuli
4a. sounds with frequencies below hearing travel through the helicotrema and do not excite hair cells
4b. Sounds in the hearing range go through the cochlear duct, vibrating the basilar membrane and deflecting hairs on inner hair cells

Describe sound transduction.

• Basilar membrane at rest: a few channels are open; cell slightly depolarized

• Hairs bent toward tallest stereocilium

• then hairs bent away from tallest stereocilium

Explain how the balance organs of the semicircular canals and the vestibule help maintain equilibrium.

• each is a flat epithelium patch containing hair cells with supporting cells

• hair cells have stereo cilia and special "true stereo cilium" called kinocilium (located next to tallest stereo cilia)

• stereocilia are embedded in otolith membrane, jelly-like mass studded with otoliths (tiny CaCO3 stones); otoliths increase membranes weight and increase its inertia (resistance to changes in motion)