EXAM 2 - AERIN 2

Question 1

1) I can describe the general organization of the spinal cord, including the arrangement of white and gray matter, spinal nerves, and the cauda equina.

Spinal cord general

Answer 1

The spinal cord is a cylinder of nervous tissue, continuous with the lower end of the brain - surrounded by the vertebral column
The inside of the spinal cord is grey matter and the outer coat is white matter (opposite of the cortex)

From superior to inferior, the spinal nerves emerge from cervical, thoracic, lumbar, sacral and coccygeal
31 pairs of spinal nerves branch off the spinal cord at regular intervals

Question 2

1) I can describe the general organization of the spinal cord, including the arrangement of white and gray matter, spinal nerves, and the cauda equina.

Cauda equina + regions

Answer 2

The spinal cord only extends about 2/3rds of the column length to the L2 vertebra
The parts that have cell bodies (grey natter)
The bottom 1/3rd of the column that contains myelinated axons, no spinal cord proper = cauda equina

A spinal tap can remove CSF or an epidural in the cauda equina can be used to avoid damage of the spinal cord.

Question 3

Cauda equina is composed of what regions?

Answer 3

Lumbar, sacral and coccygeal regions

Question 4

I can identify and describe the functions of the following structures of the spinal cord: dorsal horn; ventral horn; dorsal root ganglia; dorsal root; ventral root; and spinal nerve.

Dorsal (back) horn v Ventral (front) horn

Answer 4

Dorsal (back) horn: half of grey matter associated with SENSORY neurons (cell bodies)
Ventral (front) horn: half of grey matter associated with MOTOR neurons (cell bodies)

Question 5

I can identify and describe the functions of the following structures of the spinal cord: dorsal horn; ventral horn; dorsal root ganglia; dorsal root; ventral root; and spinal nerve.

Dorsal root ganglia, dorsal root, ventral root

Answer 5

Dorsal root ganglia: cell bodies of afferent (SENSORY) neurons found in the intervertebral foramen (not in the spinal cord itself)

• Afferent fibers originate in the periphery as sensory receptors and terminate in the dorsal horns, where they synapse on interneurons or efferent neurons

Dorsal root: the afferent (sensory) limb of each spinal nerve found in the vertebral canal

Ventral root: efferent motor limb of spinal nerves that conduct efferent (motor) impulses and are found in the vertebral column
- Project axons into the periphery
- Are in the spinal cord

Question 6

I can identify and describe the functions of the following structures of the spinal cord: dorsal horn; ventral horn; dorsal root ganglia; dorsal root; ventral root; and spinal nerve.

spinal nerve

Answer 6

Spinal nerve: less than 1 cm in length formed by the union of dorsal and ventral roots from same spinal cord level and are found in the intervertebral foramen

Question 7

I can identify and describe the functions of the following structures of the spinal cord: dorsal horn; ventral horn; dorsal root ganglia; dorsal root; ventral root; and spinal nerve.

ascending v descending bundles

Answer 7

Ascending bundles: myelinated axons carry sensory information to the brain
Descending bundles: carry commands to motor neurons

Question 8

T/F: spinal nerves are composed of the axons of both afferent and efferent neurons?

Answer 8

T

Question 9

T/F: Dorsal root ganglia contain the cell bodies of efferent neurons?

Answer 9

F

Question 10

3) I can compare the organization and function of the efferent pathways of the PNS that are composed of the somatic and autonomic nervous systems.

Pathway 1 - somatic

Answer 10

PNS → effector in muscle

Somatic - Cell bodies located in groups in the brainstem or ventral horn of the spinal cord - large diameter myelinated axons leave the CNS and pass straight to skeletal muscles where they release ACh - excitation of motor neurons leads only to contraction of skeletal muscles; there are no somatic neurons that inhibit skeletal muscles - muscle relaxation involves inhibition of motor neurons in the spinal cord

Question 11

3) I can compare the organization and function of the efferent pathways of the PNS that are composed of the somatic and autonomic nervous systems.

pathway 2 - autonomic

Answer 11

PNS → autonomic → somatic motor neurons either in sympathetic active) or parasympathetic (rest)

Autonomic neurons
- Controls glands and muscles of internal organs

• The autonomic NS is made up of 2 neurons in series that connect the CNS and the effector cells
• First neuron has cell body in CNS - second cell body is outside - autonomic ganglion
• The neurotransmitter released between pre and post ganglionic neurons - ACh
• The neurotransmitter released between postganglionic neuron and target differs between sympathetic and parasympathetic
• Signal can be excitatory or inhibitory
• ANS divided into Sympathetic and parasympathetic

Question 12

4) I can compare the general anatomy and function of the parasympathetic and sympathetic divisions of the autonomic nervous system.

Function

Answer 12

Both branches of the autonomic nervous system innervate most organs, an arrangement called DUAL INNERVATION

Sympathetic

• Most active during periods of excitation or physical activity
• Coordinates group of physiological changes known as fight-or-flight
• Includes and increase in rate or force of heart contractions, a shift in blood flow from GI organs to skeletal and cardiac muscles and energy stores are mobilized
• Inhibits digestion, etc

Parasympathetic

• Most active during resting conditions
• Stimulates the digestive organs, enhancing digestion and absorption of nutrients
• Inhibits the cardiovascular system - decreasing HR - rest-and-digest

Question 13

4) I can compare the general anatomy and function of the parasympathetic and sympathetic divisions of the autonomic nervous system.

anatomy

Answer 13

Neurons of sympathetic and parasympathetic leave CNS at diff levels

S: exit spinal cord from thoracic and lumbar regions
- Most ganglia lie close to SPINAL CORD forming the sympathetic drunk
- Sympathetic ganglia contain postganglionic nerve cell bodies give the trunk a “beaded” appearance.

PS: exist spinal cord from brainstem and sacral regions
- Lie within or close to THE ORGANS the postganglionic neurons innervate
Fibers

S: fibers leave the spinal cord in first thoracic and second lumbar segments
- Sympathetic trunks extend entire length of cord - some preganglionic axons turn to travel up or down before forming synapses

PS: in cranial portion, pregangionic original from cranial nerve nuclei located in brainstem, travel with axons in cranial nerves
- One key cranial nerve - vagus nerve carries 75% of all parasympathetic fibers (there are 2 - one on each side

Key feature of sympathetic - preganglionic neurons originate in thoracic and lumbar spinal regions

Key note: both always on, one will predominate

Question 14

5) I can identify the neurotransmitters of the PNS.

Adrenal Medulla pathway specific

Answer 14

The adrenal medulla is a modified sympathetic ganglion

Preganglionic neurons project from the spinal cord to the adrenal medulla where they synapse

Release ACH in adrenal medulla to a chromaffin cell that releases epinephrine to the blood that enters the tissues

Chromaffin cells secrete catecholamines directly into blood ( NO AXONS)
80:20 epinephrine:norepinephrine

Question 15

Neurotransmitters of PNS

Answer 15

Neurotransmitters:
- Somatic branch of PNS: ACh

• Autonomic NS
  • Sympathetic:
    ACh between pre and postganglionic cells whether in ganglion or adrenal medulla
    - Adrenal medulla pathway

Epinephrine released into blood stream and bind to Adrenergic receptors
- Spinal cord pathway

Postganglionic cell releases NE (norepinephrine) which also binds to adrenergic receptors

 - Parasympathetic: ACh for both receptors

Question 16

I can identify the receptors of the PNS.

Answer 16

Receptors:
- Somatic branch of PNS: N-AChR (@skeletal muscles)

• Autonomic NS
  a. Sympathetic: N-AChR between pre and post, Adrenergic receptors for organs

b. Parasympathetic: N-AChR for postganglionic cell, M-AChR for organ

N-AChR : nicotinic AChR - responds to nicotine

M-AChR: muscarinic - responds to the mushroom poison Atropine - competitive antagonist of M-AChR

Question 17

Agonist v antagonist

Answer 17

Agonists: molecules that bind to a receptor and trigger signalling pathways

Antagonists: molecules that bind to a receptor but DO NOT trigger signalling pathways

Question 18

Direct v indirect agonists/antagonists

Answer 18

Direct: bind to receptor
E.g. atropine

Indirect: indirectly reduces or increases neurotransmitter to bind more

Question 19

1) I can describe the basic principles of electricity in physiological systems.

Answer 19

All cells have a slight charge
Intracellular K+ high, phosphate ions + negatively charged proteins are the major anion, some protein anions inside cells do not have matching cations —> inside slightly negative

ECF - Na+, Cl-, some cations outside cells do not have matching ions that are slightly positive

Two compartments exist in a state of electrical disequilibrium

Key laws:
= Law of conservation of electrical charges
= Opposite charges attract; like charges repel each other
Separating positive charges from negative charges requires energy

Conductor versus insulator
= Conductor: when separated positive and negative charges move freely toward each other, the material through which they move is called a conductor
= Insulator: separated charges cannot move through an insulator

Question 20

2) I can describe the influence of an electrochemical gradient upon the movement of ions across a plasma membrane.

Answer 20

Plasma membranes are not permeable to ions except when channels are open

Electrical gradients are positive ions moving toward negative charged side or both

Chemical gradients are individual ion concentrations

This is created by transporters: sodium/potassium pump

Change of 1 ion creates a +1 outside, -1 inside so difference of 2

The electrochemical gradient at the resting, that potential difference is the resting membrane potential

Question 21

3) I can compare the measurement of electrical gradients using relative and absolute scales.

Answer 21

Absolute potential takes only the amount of ions moved

Relative scales is where a +1 and -1 charge means a difference of 2 so the charge is -2 resting potential because you assume the outside is 0

Electrodes are created from hollow glass tubes drawn to fine points - a recording device and a reference electrode put in

Question 22

4) I can predict the direction of movement of an ion across a plasma membrane given the concentration and charge of ions inside and outside the cell.

Answer 22

Some K+ ions leak out via channels and the - charge increases as K+ leaves because proteins are negative and cannot diffuse out

There becomes an electrical gradient - eventually the electrical force pulling the K+ in becomes equal to the K+ chemical gradient out, the net movement of K+ moves out

Question 23

5) I can calculate the membrane potential of a cell using the Nernst equation

Answer 23

The membrane potential that exactly opposes the concentration gradient of the ion is known as the equilibrium potential (Eion)

Nernst equation (ONLY 1 ION)
Eion = (61/z) log ([ion]out/[ion]in)
z=valence of the ion

Question 24

Goldman-Hodgkin-Katz (GHK) equation.

Answer 24

Goldman-Hodgkin-Katz Equation (multiple ions)

Note: Cl reversed because Cl is an anion so it has the opposite effect

K+ leak channels influence the resting membrane potential the most, but a small number of sodium leak channels are open in the resting state

The Na+/K+ pump maintains - 2 K+ in, 3 Na+ out - unequal keeps it negative

Question 25

1) I can define and accurately utilize the terms depolarization, overshoot, repolarization, and hyperpolarization to describe the direction of changes in membrane potential relative to the resting potential in an excitable cell.

Answer 25

Voltage gated channels can be: Sodium: closed, open, inactivated Potassium: Open, Closed Cycle: Na+ open → Na+ are inactivated → K+ open → Na+ closed → K+ closed Na+ cycle example of positive feedback

Question 26

2) I can discuss the properties of a graded membrane potential.

Answer 26

Graded potentials: depolarizations or hyperpolarizations that generally occur in the dendrites and cell body but DO NOT result in a flow of charge down the axon Small transient application of a chemical signal Magnitude can vary and decrease as distance increases from signal They can be summated into action potentials

Question 27

1) I can describe the threshold potential of a membrane, and the all-or-none property of and refractory periods that occur during an action potential.

Answer 27

Action potentials can only fire if they reach threshold, and if threshold is reached then an action potential will fire. There is no such thing is a half or smaller AP

Question 28

2) I can define depolarization and hyperpolarization.

Answer 28

Depolarization: membrane becomes more positive Hyperpolarization: membrane becomes more negative

Question 29

3) I can explain and identify IPSPs and EPSPs.

Answer 29

IPSP: inhibitory postsynaptic potential - hyperpolarizes membrane EPSP: excitatory postsynaptic potential - depolarizes the membrane

Question 30

5) I can explain the channel and ion movement responsible for each action potential phase.

Answer 30

Question 31

1) I can differentiate between the central and peripheral nervous systems.

Answer 31

CNS: brain + spinal cord PNS: everything else Both: neurons + glial cells Neurons: cells in nervous system that initiate, integrate, and conduct electrical signals Glia: non neuronal that maintain homeostasis and provide support – e.g. form myelin

Question 32

2) I can list the three parts of a neuron and describe their structure and function.

Answer 32

Dendrites: highly branched outgrowths of the cell body that receive most of the inputs from other neurons Cell body: contain nucleus and ribosomes – has genetic info and machinery for protein synthesis Axon: long that extends from the cell body and carries output to axon hillock where an electric signal is generated. Afferent neurons: convey info from tissues TO cns Interneurons: connect neurons WITHIN cns Efferent neurons: convey info FROM cns to tissues

Question 33

3) I can compare the different types of glial cells found in the central nervous system (CNS) and peripheral nervous system (PNS).

Answer 33

Astrocytes: support cells, control extracellular envo Microglia: immune system of CNS (like macrophages) Oligodendrocytes: form myelin – can extend to up to 50 axons Myelin is multiple concentric layers of phospholipid membrane Ependymal cells: ciliated cells that create a selectively permeable epithelial layer, the ependyma, that separates CNS fluid compartments In the PNS: schwann – can have 500 different ones + satellite cells A cluster of nerve cell bodies inside the CNS, equivalent of peripheral ganglion – nucleus

Question 34

4) I can distinguish the 3 membrane layers that surround the brain and the spinal cord.

Answer 34

Dura: thickest – associated with veins that drain blood from the brain through vessels or cavities called sinuses Arachnoid: loosely tied to inner membrane leaving subarachnoid space – CSF in subarachnoid space Pia mater: think membrane that adheres to the brain and spinal cord – arteries that supply blood to the brain are associated with this layer

Question 35

5) I can explain the process of formation, direction of flow, and functions of the cerebrospinal fluid (CSF) in the nervous system.

Answer 35

ECF formed by CSF and interstitial fluid Interstitial in pai mater Communicate with each other across blood vessels called virchow-robin spaces Choroid plexus: secretes CSF – selectively pumps sodium and solutes from the plasma into ventricles that creates an osmotic gradient that draws in water. Consists of capillaries and a transporting epithelium derived from ependyma Flows from ventricles to sub arachnoid space CSF reabsorbed by projections of arachnoid membrane called arachnoid villi CSF k2 2 things =Physical protection reduces the weight of the brain reducing pressure on blood vessels and nerves and provides protective padding = Chemical protection for regulated ECF

Question 36

6) I can compare the movement of molecules across the endothelial cells of typical peripheral capillaries to the endothelial cells of CNS capillaries.

Answer 36

BBB formed by tight junction endothelial cells stimulated by paracrine signals from astrocytes Tight junctions prevent solute movement between cells Need to do transcytosis if hydrophilic Endocytosis into the cell and exocytosis out in normal cells Most hydrophobic diffuse across endothelial cells Transcytosis does not occur across capillary endothelial cells in CNS The movement of hydrophilic molecules across capillary walls is restricted so TRANSPORT PROTEINS are key

Question 37

1) I can locate the three main parts of the human brain, including the forebrain, the brainstem, and the cerebellum, on a diagram.

Answer 37

Forebrain - Cerebrum - Diencephalon - Thalamus - Hypothalamus - Pituitary gland Brainstem - Midbrain - Pons - Medulla oblongata

Question 38

what about the cerebellum? and function

Answer 38

Cerebellum Receives sensory info about position from the spinal cord, motor information from the cerebral cortex and info about balance Transmits info to the cortex via thalamus enabling the cortext to alter output to smooth movement

Question 39

2) I can describe the structure, organization, and function of the forebrain including the cerebrum and the diencephalon (thalamus and hypothalamus). cerebrum

Answer 39

Cerebrum Left and right separated by longitudinal fissure Connected by a bundle of nerve fibers called corpus callosum Deep subcortical nuclei on underside (i.e basal nuclei k2 planning and executing movement) Cerebral cortex: grey matter composed of cell bodies and inner layer of white matter composed of myelinated fiber tracts 6 key layers and sulci allow for increased SA without increased volume Sensory info does not enter the cortex DIRECTLY Regions k2 information output have large layer 5 pyramidal neurons Lots of different functions and can be mapped topographically

Question 40

2) I can describe the structure, organization, and function of the forebrain including the cerebrum and the diencephalon (thalamus and hypothalamus). Diencephalon

Answer 40

Central core of forebrain Composed of Thalamus Cluster of cell nuclei where all sensory information follows a pathway taht induces a direct relay through the thalamus Info Filtered in here Damage can cause synesthesia which results in involuntary experiences in second sensory or cognitive pathway Hypothalamus Has cell groups and pathways that form the master command center for neural and endocrine coordination

Question 41

3) I can identify and describe the general functions of the brainstem structures (including the midbrain, pons, and medulla oblongata) and the cerebellum.

Answer 41

Loosely arranged neuron cell bodies intermingled with bundles of axons : reticular formation Midbrain: k2 motor control and vision/eye sight - l2 sensory and motor integration Pons: breathing, swalling, balalnce, k2 relaying signals Medulla Oblongata: controls heartbeat, breathing, blood pressure

Question 42

Answer 42

a. label D b. label A c. label C d. label B

Question 43

Answer 43

A: thin B: Thick C: thin + thick

Question 44

Describe anatomy of sarcomere

Answer 44

a) A band extends the length of the thick filament and includes a portion of the thin filament b) I band area between the ends of the thick filaments; contains only thin filaments c) H zone areas between the ends of the thin filaments; contains only a portion of the thick filaments - The H zone is located in the middle of the A band. The H zone contains only thick filaments. The A band consists of thick and thin filaments. The H zone is a subset of the A band d) Z disc vertical line at each end of the sarcomere located in the middle of the I band e) M line vertical line in the middle of the H zone that connects the thick filaments together

Question 45

2) I can explain length relationships between relaxed and contracted sarcomeres.

Answer 45

Length of thin and thick do not change Length of A: doesnt change Length of I: reduces Length of H: reduces Length of Sarcomere: reduces A sarcomere shortens when the thin filaments and thick filament overlap to a greater extent. The filaments do not shorten, but overlap, causing a shortening of the sarcomere as a whole.

Question 46

Why is there a limit to the amount of shortening that can occur in a sarcomere during muscle contraction?

Answer 46

Depending upon the length of the thin filaments, there is a limit to the amount of overlapping that can occur between the thick and thin filaments. Also, the Z discs may run into the ends of the thick filaments and not be able to shorten any further.

Question 47

2) I can explain the four steps of the Myosin activity cycle.

Answer 47

Myosin activity cycle: 1. ATP binding causes detachment of myosin head from actin filament - in rigor without ATP 2. ATP hydrolysis results in the head moving to the ‘cocked’ position, the angle of the head changes and binds weakly to the filament 3. The binding of the head to actin results in conformational change releasing he inorganic phosphate 4. Power stroke - release of inorganic phosphate initiates the power stroke that forcibly returns the head to its cocked position, release of ADP follows rapidly

Question 48

3) I can describe the relationship of the molecules troponin/tropomyosin with Ca2+ concentration in the skeletal muscle cytoplasm.

Answer 48

Troponin + tropomyosin respond to calcium signalling to regulate muscle contraction Troponin: made up of 3 subunits including Ca2+- binding, TnC subunit Tropomyosin: rod shaped protein that overlaps with 7 actin monomers, covering myosin-binding sites

Question 49

describe Ca2+ effect on tropomyosin+troponin

Answer 49

An increase in muscle cell cytoplasmic [Ca2+] triggers coordinated Actin/Myosin 2 interaction Binding of Ca2+ to troponin results in a conformational change that shifts tropomyosin to a position that reveals the myosin binding sites on the actin filaments

Question 50

4) I can list and explain the steps required for excitation-contraction coupling in skeletal muscle.

Answer 50

Cycle: 1. An AP stimulates the muscle 2. A muscle AP follows the t tubules deep into the muscle fiber 3. This stimulates the release of Ca2+ from the sarcoplasmic reticulum 4. Together, Ca2+ and ATP are required for thin-thick filament contraction 5. When the electric potential of the muscle plasma membrane returns to normal, Ca2+ is pumped back into the sarcoplasmic reticulum by powerful Ca2+ pump proteins

Question 51

Calcium release mechanism specific

Answer 51

AP triggers conformational change in a voltage-sensitive protein DHP (dihydropyridine receptor) in the t tubule which triggers opening of ion channels (ryanodine receptors on the sarcoplasmic reticulum, releasing Ca2+ into the cytoplasm

Question 52

1) I can describe the threshold potential of a membrane, the all-or-none property of and refractory periods that follow an action potential.

Answer 52

Absolute refractory period occurs when voltage-gated Na+ channels are already open or have proceeded to the inactivated state. The inactivation gate has blocked these channels and must be removed by membrane repolarization, closing the pore before the channels can reopen to the second stimulus After absolute = relative refractory period when a second AP could be produced but only if the strength is CONSIDERABLE

Question 53

2) I can describe the unidirectional propagation of an action potential down an axon, from trigger zone to axon terminal.

Answer 53

Summated graded potentials at the trigger zone, which creates an action potential which travels down the axon - the AP at the trigger zone is equal to the AP at the end of the axon - no loss of energy Spreads via local current and repelled by the Na+ that entered before it Cannot go backwards because any charge does not depolarize due to inactivated Na+ channels in absolute refractory

Question 54

3) I can compare the propagation of action potentials in unmyelinated and myelinated axons.

Answer 54

Unmyelinated axons have low resistance to current leak because the entire axon membrane is in contact with the extracellular fluid and has ion channels through which current can leak Myelinated axons limit the amount of the membrane in contact, only the does of ranvier are in contact, the rest are wrapped in walls that resist ion flow out = This increases speed of the AP = Each node has a high concentration of channels = The “jump” of AP is called saltatory conduction

Question 55

4) I can compare the structure and function of electrical and chemical synapses.

Answer 55

Electrical synapses occur mainly in neurons of the CNS Info can flow in both directions through gap junctions - rapid conduction of signals that synchronizes activity Chemical synapses are the vast majority used in the nervous system, pass from pre to post synaptic cells In between: synaptic cleft Physical separation results in one way conduction

Question 56

5) I can discuss the role of Ca2+ in regulating neurotransmitter release at a chemical synapse.

Answer 56

Process of transmission - Within the presynaptic active zone, synaptic vesicles contain neurotransmitter - The post-synaptic density is a protein dense region in the postsynaptic membrane in close apposition to the presynaptic active zone ensuring that receptors are in close proximity to the neurotransmitter release sites 1. AP reaches terminal 2. Terminals possess voltage gates Ca2+ channels that open during depolarization allowing Ca2+ to flow into the axon terminal 3. Ca2+ activates processes that lead to fusion of docked vesicles 4. Ca2+ binds to synaptotagmin proteins associated with SNARE proteins that anchor vesicles and undergo Ca2+ dependent conformational changes to stimulate vesicle fusion 5. After fusion, vesicles either A. fuse completely with the membrane and are recycled by exocytosis later B. fuse only briefly and release contents then withdraw (kiss-and-run fusion - common w high frequency)

Question 57

How are unbound neurotransmitters removed?

Answer 57

1. Diffuse away from receptor site 2. Enzymatically transformed into inactive substances (may be transported back to axon terminal for reuse) 3. Are actively transported back into presynaptic axon terminal (reuptake) or into glial cells

Question 58

6) I can compare the characteristics of smooth or cardiac muscle tissue to skeletal muscle tissue.

Answer 58

Skeletal muscles are connected to at least 2 bones Connected via tendons

Question 59

7) I can describe the hierarchical organization of skeletal muscle into fasicles, muscle fibers, myofibrils, and sarcomeres.

Answer 59

Muscle wrapped in epimysium - Within muscle, fascicles wrapped in perimysium - Within fascicles, muscle fibers (e.g. muscle cells) wrapped in endomysium - Within muscle fibers, the plasma membrane is called the sarcolemma with sarcoplasm - in sarcoplasm is myofibrils with contratole machinery - Within myofibrils, there are sarcomeres Sarcomeres are made up of thin (actin) and thick filaments (myosin)

Question 60

8) I can describe the relationship of sarcomere structure and skeletal muscle contraction.

Answer 60

Myosins are a class of motor proteins that use actin filaments as a substrate Myosin 1 - carries substrates as a single unit Myosin 2 - forms a dimer Each head of myosin has an actin-binding site and an enzymatic domain that hydrolyzes ATP

Question 61

what is sliding filament theory

Answer 61

Sliding filament theory: contraction is caused by a simultaneous shortening of all the sarcomeres, no change in length of either filament

Question 62

I can define the term motor unit.

Answer 62

Motor neuron cell bodies are located in the ventral horn of the spinal cord or in the brain stem - motor neuron axons are myelinated and are the largest diameter axons in the body Motor neurons therefore propagate APs at high velocities Motor unit: a motor neuron + the fibers it innervates muscle fibers - muscle fibers in a single motor unit are located in one muscle but they are scattered throughout the muscle All muscle fibers in a unit contract when neuron sends AP 1 neuron, many fibers

Question 63

2) I can compare interneuronal synapses and the synapses between motor neurons and skeletal muscle fibers called neuromuscular junctions (NMJs).

Answer 63

NMJ features: Myelin shealth ends near the surface of a muscle fiber and the axon divides into a number of short processes that lie in the grooves on the muscle fiber surface Neurotransmitter: ACh NMJ: the junction of an axon terminal with the muscle fiber plasma membrane (the motor end plate) 2 key differences between interneuronal synapses and NMJ: 1. The magnitude of a single depolarization of a motor end plate (EPP - end plate potential) is much larger than an excitatory graded potential (EPSP) because at an NMJ, neurotransmitter release is over a larger area, binding to and opening more N-AChR - every AP in a motor neuron produces an AP in each muscle fiber in the motor unit - that is not true in interneuronal synapses 2. IPSPs do not exist in skeletal muscle

Question 64

Disruption in Neuromuscular signalling

Answer 64

Tubocurarine: neuromuscular blocking agent - muscle relaxant Nicotinic ACh receptors on motor end plate

Question 65

3) I can name and describe the key components of the circulatory system. Blood + circulatory systems

Answer 65

Key components 1. The blood (fluid to be moved) 2. The heart (the pump) 3. The blood vessels (the pipes) The blood is made up of “formed elements” (cells and cell fragments) suspended in plasma (mostly water) 1. Plasma makes up 50 percent of blood volume 2. Leukocytes and platelets make up buffy coat 3. Hematocrit, % blood that is erythrocytes - 42-45 percent Erythrocytes = red blood cells that carry h20 and o2 - Decreased in women The heart is divided into 2 halves, each with 2 chambers (upper = atrium, lower = ventricle). Blood flows from the atrium to the ventricle. Blood does not pass between the sides of the heart. Pulmonary circuit: deoxygenated blood goes from Right atrium -> right ventricle -> lungs where it gets blood -> left atrium Systemic circuit: oxygenated blood moves from left atrium -> left ventricle via aorta -> tissue -> empties in right atrium via superior and inferior vena cava

Question 66

3) I can name and describe the key components of the circulatory system. Blood vessels

Answer 66

The vessels can be divided into arteries, arterioles, capillaries, venules and veins Arteries carry blood away from the heart Arterioles connect arteries and capillaries Capillaries exchange oxygen with tissues Venules connect capillaries and veins Veins carry blood towards the heart

Question 67

I can describe the relationship of pressure and resistance upon blood flow in the circulatory system.

Answer 67

Liquid flows down pressure gradients - contraction and relaxation is used for this Overall: highest pressure in aorta and arteries, and lowest mean pressure is venae cavae As blood flows pressure is lost due to friction between fluid and walls

Question 68

How to calculate pressure difference

Answer 68

Delta P = P1-P2 Measured in mmHg Higher pressure gradient, the greater the flow Flow (F) = delta P / R R = resistance to flow Influenced by the radius of the tube (r, the length of the tube (L), the viscosity of the liquid (n) R= 8 Ln / pi r^4

Question 69

vaso constriction v dilatioon

Answer 69

Vasoconstriction: a decrease in blood vessel diameter that decreases blood flow through the vessel Vasodilation: increase in blood vessel diameter that increases blood flow through the vessel

Question 70

how do myocardial cells recieve oxygenated blood

Answer 70

Myocardial cells receive blood supply via coronary arteries which lead to branching network of small vessels same as other organs - most cardiac veins empty into coronary sinus that empties into the right atrium.

Question 71

Heart valves ensure one way flow through the heart - AV

Answer 71

The left AV valve (Mitrial) - has 2 flaps and is called bicuspid The right AV valve has 3 flaps and is called the tricuspid These are the AV atrioventricular valves that act as one way valves permitting the flow of blood from atria to ventricles only. Interventricular septum separates the two ventricles

Question 72

Semilunar valves

Answer 72

Opening of right ventricle into the pulmonary trunk (pulmonary artery) Opening of left ventricle into the aorta Prevent blood the opposite way All valves act passively

Question 73

I can describe the structure of the heart including cellular composition

Answer 73

Outerlayer of the heart - pericardium Inner layer of the heart - epicardium In between fluid that serves as a lubricant The wall of the heart is the myocardium and is composed of cardiac muscle cells. Cardiac muscle cells are arranged in tightly bound together layers that completely encircle the blood-filled chambers - each cell contracts with every beat of the heart so these cells do not get much rest and have intercalated disks with gap junctions to ensure a functional syncytium to function as a unit The inner layer of the cardiac chambers is lined by a thin layer of endothelial cells

Question 74

1) I can compare the membrane permeability underlying a neuronal action potential with the underlying depolarization events in cardiac cells. Cardiac muscle cells

Answer 74

Unique to cardiac cells, Long-lasting (L)-type Ca+ channels open, and remain open for a long period of time. This Ca+ influx keeps keeps the membrane depolarized at the plateau level

Question 75

1) I can compare the membrane permeability underlying a neuronal action potential with the underlying depolarization events in cardiac cells. SA node cells

Answer 75

SA node cells because they are spontaneously generate their own APs and do not have steady resting potentials Have a unique set of channels that open when membrane potential is at negative values called Funny (F)-type channels

Question 76

2) I can describe the basic components of an electrocardiogram (ECG) and what each waveform represents.

Answer 76

3 major readings: P wave, QRS complex, T wave P wave: atrial depolarization Between p and qrs: atrial depolarization complete, impulse delayed at AV node QRS complex: Ventricular depolarization, atrial repolarization Between QRS and T: ventricular depolarization is complete T wave: ventricular repolarization

Question 77

i can analyze normal and abnormal readings venticular tachycardia

Answer 77

tachycardia: faster than normal bradycardia: slower than normal normal: 60-100 bpm

Question 78

i can analyze normal and abnormal readings blockages

Answer 78

Question 79

how to calculate bpm

Answer 79

determine the amount of seconds on the boxes (likely 60) and then just count

Question 80

which part of the intrinsic electrical system serves as the normal pacemaker for the heart.

Answer 80

SA node because it has the fastest rate of firing action potentials.

Question 81

Model 2 shows the pathway of electrical excitation that passes over the heart (darkened areas in the diagram indicate electrical excitation). In some areas the electrical activity spreads via the specialized conducting cardiac muscle cells. In other areas action potentials spread from one cardiac muscle fiber to the next through specializations in the cells’ membranes called gap junctions. Question: As a team, examine Model 2 and describe what is happening in each of the figures. Include the names of specific electrical system structures when they are involved. Figures A and B are described to get you started. A: rest (no electrical excitation) B: SA node has generated an action potential which is starting to spread over the atrial muscle mass C: D: E:

Answer 81

A: rest (no electrical excitation) B: SA node has generated an action potential which is starting to spread over the atrial muscle mass C: atrial myocardium and AV node are excited D: excitation has passed through the AV node into the AV bundle and bundle branches E: excitation has passed through the Purkinje fibers into the ventricular walls so that now all of the ventricular myocardium is excited.

Question 82

a) Calculate the heart rate (bpm). b) What is the heart rhythm? c) Are all of the waveforms present? d) Are the waveforms normal or abnormal? If abnormal, how?

Answer 82

a) Heart rate = 80 beats per minute (BPM). This is a normal heart rate (60‐100 bpm). b) Rhythm of QRS complexes is irregular. c) P wave rhythm is regular and (d) P waves are normal, but occasionally not followed by QRS complexes. This is an example of Second Degree Heart Block Type I involving a disease of the AV node. This is almost always a benign condition for which no specific treatment is needed. In symptomatic cases, intravenous atropine or isoproterenol may transiently improve conduction.

Question 83

a) Calculate the heart rate (bpm). b) What is the heart rhythm? c) Are all of the waveforms present? d) Are the waveforms normal or abnormal? If abnormal, how?

Answer 83

a) Heart rate = 110 beats per minute (BPM). This is a fast heart rate (>100 bpm) = tachycardia. b) Rhythm is irregular. c) No (d) P waves cannot be identified. This is an example of atrial fibrillation. The atria are undergoing chaotic, quivering contractions that are out of coordination with the ventricles. There is an absence of an isoelectric baseline.

Question 84

a) Calculate the heart rate (bpm). b) What is the heart rhythm? c) Are all of the waveforms present? d) Are the waveforms normal or abnormal? If abnormal, how?

Answer 84

a) Heart rate = 130 beats per minute (BPM). This fast heart rate (>100bpm) = tachycardia. b) Rhythm is normal. c) Yes, the waveforms are all present. d) P waves, QRS complexes, and T waves are normal. This example = Sinus Tachycardia. Sinus tachycardia is a fast rhythm with sinoatrial node impulses greater than 100 beats per minute. Heart rate varies normally with age, with infants and young children having fast rates. Sinus tachycardia is a normal response during exercise and when under stress. Many other factors will cause sinus tachycardia including heart failure, COPD, fever and stimulants.

Question 85

what is systole and diastole

Answer 85

Systole: ventricular contraction phase involving blood ejection Diastole: ventricular relaxation involving blood injection to the heart

Question 86

Systole has 2 discrete periods:

Answer 86

Isovolumetric ventricular contraction - first part of systole, ventricles contracting but valves are closed so blood volume is constant while pressure increasing Ventricular ejection - second part of systole, the semilunar valves open and blood is forced into the aorta and pulmonary artery , once the pressure exceeds that of the aorta and pulmonary artery, blood is ejected (STROKE VOLUME = SV)

Question 87

Diastole has 2 discrete periods:

Answer 87

Isovolumetric relaxation - the ventricles begin to relax and the semilunar valves close, the AV valves are also closed so pressure is decreasing but the volume of blood is not changing Ventricular filling - the AV valves open and blood flows from atria to ventricles - atrial contraction occurs at the end of diastole after most filling has occurred. ~80% of filling occurs before atrial contraction

Question 88

describe cardiac cycle via wigger diagram

Answer 88

Question 89

describe the changes in aortic pressure via the wigger diagram

Answer 89

- aortic pressure is higher than ventricular pressure during diastole because the aorta is able to store pressure during systole that can be released during diastole - the aorta stores this pressure, because during systole, the aortic walls are stretched by entering blood which can store pressure and when the blood leaves and pressure falls, the wall recoils, releasing the energy stored which drives blood through downstream vessels even though no blood is being ejected from the heart at this time - this ensures blood flows continuously

Question 90

calculations for end systolic volume, end diastolic volume, and stroke volume

Answer 90

Question 91

If chamber A represents the left atrium and chamber B represents the left ventricle, what are the valves

Answer 91

a) Valve 1: left A-V valve (bicuspid valve) b) Valve 2: left semilunar valve (aortic valve) c) Chamber C: aorta

Question 92

When the left ventricle pumps blood into the aorta, the left ventricular pressure is __________ aortic pressure.

Answer 92

greater than

Question 93

The aortic (left semilunar) valve is ____________ when the left ventricle pumps blood into the aorta.

Answer 93

open; Left ventricular pressure > aortic pressure so aortic valve is open and blood is flowing through it.

Question 94

The left A-V (mitral) valve is ____________ when the left ventricle pumps blood into the aorta.

Answer 94

closed; the mitrial valve is closed to prevent back flow of blood into the left atrium

Question 95

When the ventricle is filling with blood, the left ventricular pressure is __________ left atrial pressure.

Answer 95

When the ventricle is filling with blood, the left ventricular pressure is less than left atrial pressure. Blood flows down a pressure gradient.

Question 96

a. Pressures are shown for which three locations in the cardiovascular system in Model 2? b. Which of these locations has the lowest pressure throughout the cardiac cycle? c. Which of these locations shows the greatest change in pressure during the cycle?

Answer 96

a. aorta, left ventricle, left atrium b. left atrium c. Left ventricle

Question 97

Using the small letters a-f on the pressure recordings in Model 2 indicate each of these events and intervals in a cardiac cycle: i) the beginning of (ventricular) systole b ii) the beginning of (ventricular) diastole e iii) the interval representing systole b-e iv) the interval representing diastole e-b

Answer 97

Answer 1: Correct! b Answer 2: Correct! e Answer 3: Correct! b-e Answer 4: Correct! e-b

Question 98

Individually, determine the pressure relationship between the atrium and the ventricle across the mitral valve at points b, c, e, and f

Answer 98

Question 99

Is the mitral valve open or closed during interval c-e?

Answer 99

Pventricle > Patrium so the mitral valve is closed.

Question 100

Is the aortic valve open or closed during interval c-e?

Answer 100

Pventricle > Paorta so the aortic valve is open.

Question 101

Are there times during the cardiac cycle that both the mitral and aortic valves are closed? If no, why not? If yes, when and what is happening during these times?

Answer 101

Both valves are closed during the short early stage of systole (b-c in Model 2; isovolumetric ventricular contraction) and the short early stage of diastole (e-f in Model 2; isovolumetric ventricular relaxation). With both valves closed no blood flows into or out of the left ventricle; its volume remains unchanged. However, pressure within the ventricle changes rapidly and dramatically during these short periods.

Question 102

When is the left ventricle filling with blood in Model 2? Indicate the interval using the appropriate letters a-f.

Answer 102

f-b of next cycle when Patrium > Pventricle and the mitral valve is open. This period is called ventricular filling.