Domestic Animal Physiology Exam 2

Central Nervous System

The part of the nervous system that includes the brain and spinal cord.

It processes information and coordinates responses throughout the body.

It receives messages from the PNS and sends instructions through nerves to muscles and glands

INTEGRATED: processes and combines info from diff sources

Peripheral Nervous System (everything outside CNS)

Cranial nerves and spinal nerves

Connect the CNS to the rest of the body

SPLITS into motor and sensory divisions

Sensory division (derived from PNS)

carries info to CNS

senses sensory stuff like temp, pressure, pain, touch
—> receptors to CNS

AFFERENT: arrives at CNS

Motor division (derived from PNS)

carries instructions away from CNS to muscles and glands to cause reaction

causes us to do something

*feel something hot, make hand move away

EFFERENT: exists CNS

splits into autonomic and somatic

Somatic (derived from motor)

things we DO control (running away, walking, moving)

Autonomic AUTO (derived from motor)

things we don’t control (breathing, heartbeat)

SPLITS into sympathetic and parasympathetic

Sympathetic (derived from autonomic)

fight or flight

activates body during stress, danger, excitement

—> increases heart rate, prepares muscles for action

—> triggers release of epinephrine (adrenaline)

Parasympathetic (derived from autonomic)

relaxation

calms body, recover

supports digestion and energy consumption

slows heart

horse grazing and digesting

Neurons/nerve cells

carry the electrochemical gradient

Neuroglial (type of neuron)

GLUE

keep the other cell types functioning

supportive cells to nervous tissue

6 types: 4 CNS, 2 PNS

Astrocytes (CNS, neuroglial) house keepers

most abundant

shy of 50% of cells

FORM: blood brain barrier, provide nutrients, transmitters

HOUSEKEEPERS

alzheimers and dementia

Microglia (CNS, neuroglial) dentist

10-15% of cells

removes plaque and dead or damaged neurons

Ependymal (CNS, neuroglial) spine production

help produce cerebrospinal fluid and lines the spinal column

help with neuroregeneration

Oligodendrocytes (CNS, neuroglial) myelination

helps with and keeps signals, on axon

Schwan cells (PNS, neuroglial) myelination

also on axon, helps keep signals

axon insulation

Satellite (PNS, neuroglial) circles to see if regenerative

Neuroregenerative cells, when a neuron is damaged, will help repair

Dendrites (neuron component)

Receptive region on axon

receives signals from other neurons

tree branches

Cell body or soma (neuron component)

nucleus

maintain cell and make proteins

Axon/terminals (neuron component)

extends from soma

carries signals to parts of body

millimeters to meters long

one of the first visible parts w/o micro

electrochemical gradient—> away from soma

axon hillock (neuron component)

where soma and axon meet

where threshold must be met

Axon (neuron component)

carries action potential away from soma (tail)

short or long

Axon terminals (neuron component)

at the end of axon

releases transmitters that talk with the other neurons, glands, and muscles

Myelin sheath (neuron component)

Insulates the axon with oligodendrocytes and Schwann cells

helps signal travel faster

Excitability (neuron communication property)

neuron gets excited

responds to a stimulus by changing electrical state

could be membrane voltage

Conductivity (neuron communication property)

Has to pass excitability down along with an electrochemical gradient (electrical signal down axon)

towards terminals

Secretion (neuron communication property)

in charge of releasing transmitters (signals) to the next cell

Action potential

how/what the signal starts as

pass or fail

must meet threshold at hillock and push down axon

Ligand-gated channels (type of action potential)

opens when a transmitter binds to the channel or its receptor

Chemical door OPENS

sodium now begins to flow into cell

Mechanically-gated channels (type of action potential)

A physical change is needed to open the channels

like pressure or temp in the surrounding areas of the membrane

will change the ions to be sensed by your brain

Voltage-gated channels (type of action potential)

opens as a response to a change in the membranes potential

measured in voltage

action potential baseline

Resting membrane potential

-70 millivolts

The inside of the neuron is more negative than the outside because of K+ and proteins vs. all sodium

resting - action - resting

Voltage-gated channels are closed

getting ready to receive signal

depolarization (+30 millivolts)

-70 —> +30

Action potential reaches threshold

voltage gated sodium channels open and sodium flows in, replacing negative with positive

Na mixes with K

Repolarization (back to -70)

starts becoming more negative again

Na channels become inactivated (stops letting it in, ball and chain clog channel)

K channels open and K starts leaving the axon

less positive is being let in and positive is leaving = more negative

Hyperpolarization (dips below -70)

goes below resting

k channels are slow to close, so more and more gets let out and goes super negative

but has to return to resting point by ATPase pump

ATPase pump (sodium and potassium pump) 3 and 2

in order to return to -70

this pump physically pushes sodium and potassium back into the acon

pushes 3 Na and 2 K

this opens Na channels back up

Absolute refractory (when depolarization is at peak)

there can be no more action potentials or signals taken at this time

allows sodium channels to reset

helps keep signals going the right way down the axon

Relative Refractory (during repolarization to hyper)

Would have to take a very strong signal for another AP to be accepted

it’s returning to resting point and could take another signal

Stimulus decay

if threshold isnt met cause signal is too weak

voltage change fades away

all or nothing

has to meet threshold

Myelination (insulatin)

fatty covering around axon

myelin sheath helps signals travel faster

80% fat

20% protein

Myelination advantages WAVE

signals occur at the myelin sheath gaps (nodes of rainer) and then travels underneath sheath again

this makes sure signal doesn’t have to stop at each part of the neuron and regenrate AP

like the wave

Propagation of action potential (how it travels)

• AP starts

• stimulates next section

• the section behind is refractory so another signal can’t cause a AP unless very strong

• signal moves forward, since behind is less liekly to fire to it keeps going

Oligodendrocytes (CNS, myelination)

oligo: MANY dendrites: tree braches

can form many myelin around multiple axons

extension

Schwann (PNS, myelination)

one segment of myelin around the axon

multiple to cover long axon

balls

Synaptic signaling

functional connection between a neuron and another cell

Chemical synapses (synaptic signaling type)

Like a text message

Uses transmitters sent from a neuron to interact with other cells

Released from terminals, crosses a small gap, and binds to receptors and causes a response

Electrical synapses (synaptic signaling type)

like airdrop almost

passes electrical signals to close together cells

very quick

gap is very small in between neuron and cells

Axodendrites (synaptic relationship)

the axon terminals from the pre-synaptic connects to the dendrites of the post synaptic

Axosomatic (synaptic relationship)

the axon terminals from the pre connect with the soma from the post

Axoaxonic

the axon terminals from pre connect with the axon terminals from post

Synaptic signaling (calcium)

neuron —> transmitters —> cells

1. AP reaches threshold

2. voltage gated Ca channels open, Ca floods

3. Ca triggers synaptic vesicles to release transmitters and fuse to plasma membranes

4. Then transmitters are released by exocytosis and released into the synaptic gap

What happens when transmitters are released

after they bind to the ion channel on the receiving cell

• ion channels open up allowing Na to flow

• cell volatge changes

• graded potentials differ in size

• if threshold is met, AP sent

Reuptake (when a AP needs to end)

the neuron takes it back into the axon terminals to be reused at a later time

Enzymatic degradation (AP needs to end)

an enzymes breaks down the transmitter to it cant be sent

Diffusion (when AP needs to end)

transmitter just drifts away from synaptic cleft, no longer available to bind to receptors

Smooth muscle (muscle type)

the most different

makes up hollow organs (stomach, urinary bladder, intestines)

not striped

1 nucleus per each cell

involuntary

move substances through digestive system

Skeletal muscle (muscle type)

longest fiber type

striped (striated) their contractile units are lined up in an organized pattern

voluntary (things like walking, moving, lifting)

contract rapidly - produces movement

MULTIPLE nuclei per cell

POWERFUL: strong contractions

Cardiac Muscle (muscle type)

only in the heart

striated

involuntary

self regulates

1-3 nuclei per cell

Functions of the muscles (4)

• produce movement

• maintain posture

• stabilize joints

• create heat

Muscle characteristics (5)

• Responsiveness: has to be able to respond

• conductivity- carries the signal along the muscle fibers

these 2 are signaling

• contractility- contracts

• elasticity- can return to shape after being stretched

• extensibility- muscle can stretch without being damaged

how the muscle moves

How skeletal muscles develop

embryonic mesoderm cells —> myoblasts —> myotube —> satellite —> mature skeletal muscle fiber

once they are born they dont make any more cells

Myoblasts (skeletal muscle development)

early muscle cells that join together

embryonic cells

undergo cell division to increase the number of cells to enlarge

hyperplasia

Myotube (functional contractile unit of skeletal muscle)

several myoblasts fused together to form skeletal muscle fiber

myotube matures into muscle

Hyperplasia

an increase in the number of cells

pre birth

myoblasts in embyro

Hypertrophy

an increase in the size of cells

post birth

myotubules and muscle fiber

Muscle components

the muscle — wrapped in epimysium

the fascicle — wrapped in perimysium

each individual muscle fiber — wrapped by endomysium

myofibrils — muscle contractions

sacromeres — force producing in striated

myofilaments — make up muscle fibers

actin and myosin

Organells inside a muscle cell

glycoside

sarcolemma

sarcoplasm

sarcoplasmic reticulum

terminal cisterns

transverse tubules

Glycoside (in muscle cell)

glycogen storage

Sarcolemma (in muscle cell)

barrier (plasma membrane)
pass electrical signals down the plasma membrane, conductivity that can occur within the sarcolemma.

Sarcoplasm (in muscle cell)

cytoplasm, extracellular matrix

Sarcoplasmic Reticulum (SR) (in muscle cell)

makes proteins and mRNA
the end of each one there are terminal cisterns

Terminal Cisterns (in muscle cell)

stores calcium

Transverse Tubules (T tubules) (in muscle cell)

recieves signals from sarcolemma and gives it to terminal cisterns

conduct the electrical signal from the sarcolemma to the terminal cisterns

 has openings, that's where the connection is made

Triad (in muscle cell)

2 terminal cisternae and 1 transverse tubule

• The “triad”

• For these 3 parts

• These lineup throughout the muscle fiber

Glycogen (in muscle cell)

in the sarcoplasm

provides fuel for making ATP which muscles need for energy to contract

Structural components

myofilaments

I bands

Sacromere

Myofibrils

Myofilaments

ACTIN and MYOSIN

THIN and THICK’

in the myofibril

I bands

• forms what's known as the sarcomere

Sacromere

• The functional unit actually contracts within the muscle. Uses actin and myosin to do so

Myofibrils

• Take up 80% of the space. Why nuclei shoved to the surface. Muscle uses a significant amount of energy (ATP)

myofilaments are in here

Muscle Twitch (how muscle contracts)

Muscle response to a single, brief threshold stimulus

3 phases

uncontrolled

GRADED RESPONSE

Latent Period

excitation and contraction coupling

brief delay between the arrival of a nerve stimulus and the actual beginning of a muscle contraction

stiulating muscle to start contraction

nerve needs to signal muscle and muscle must release Calcium for muscle to contract

gets it all prepped to contract

Latent period movement described

1. nerve sends signal

2. AP travels to terminals

3. Ca channels open

4. causes vessicles to fuse with the nerve and release ACh

5. ACh crosses synaptic cleft

6. ACh binds to ligand gated channels on muscle fiber

7. MUSCLE RECIEVES SIGNAL

8. once ACh binds, Na moves into muscle fiber

9. changes membrane potential (depolar)

10. if AP passes threshold then it travels down sarcolemma

11. travels down T tubes intoo muscle fiber

12. triggers Ca release from SR into sarcoplasm

13. activate muscle fibers

14. tension high

Period of contraction

cross bridge cycle

increase in tension

Period of contraction movement described

1. one calcium enters sarcoplasm and allows the proteins to interact

2. 4 proteins (actin, myosin, tropomyosin, and troponin)

3. actin slides towards middle of sarcomere

4. myosin heads attach to actin

5. cross bridge (myosin grabbing actin, pulling it, relasing it and resetting) contraction

6. ADP and phosphate are released and tension is produced

7. ATP binds to myosin and allows it to release actin

8. ATP breaks down and allows myosin to reset

9. Cycle repeats

Cross bridge cycle

The 4 Steps of the Cycle

1. Cross-Bridge Formation (The Grab)

   • Calcium floods into the muscle cell and binds to a protein called troponin.

   • This moves tropomyosin out of the way, exposing the binding sites on actin.

   • The energized myosin head (holding ADP and an inorganic phosphate, \(P_{i}\)) attaches firmly to actin, forming a cross-bridge. [1, 2]

2. The Power Stroke (The Pull)

   • The inorganic phosphate (\(P_{i}\)) is released.

   • This release triggers the myosin head to pivot sharply, pulling the actin filament toward the center of the sarcomere (the muscle unit).

   • ADP is then released from the myosin head. [1, 2]

3. Cross-Bridge Detachment (The Let-Go)

   • A new molecule of ATP binds to the myosin head.

   • This forces the myosin head to weaken its grip and detach from the actin filament. (Without fresh ATP, the muscle gets stuck in a rigid state called rigor mortis). [1, 2]

4. Reactivation (The Reset / "Cocking")

   • The myosin head breaks down (hydrolyzes) the newly attached ATP into ADP and \(P_{i}\).

   • The energy released from this breakdown resets the myosin head back into its high-energy, "cocked" position—ready to grab the next spot on the actin filament. [1]
     
     This continues until we run out of Calcium, and this is where you enter the relaxation period

Period of Relaxation

• decrease in tension back to zero

Period of relaxation movement explained

1. nerve stimulation stops, nerve stops releasing ACh and acetylcholinesterase removes ACh

2. Ca returns into the SR

3. tropomyosin covers actin again

4. tension decreases, myosin can no longer form new cross bridges so the muscle stops actively pulling and relaxes

Graded Muscle Response

how your body changes the strength of a muscle contraction so it matches what you are trying to do

1. recruit more motor units to increase tension
To lift something light, your brain activates only a few motor units. To lift something heavy, your brain recruits more and more motor units until the whole muscle pulls with maximum force. This is called recruitment

2. increase frequency of signal and stimuli

If a muscle gets a single signal, it does a quick, weak twitch and then relaxes.

• If signals arrive rapidly—before the muscle can fully relax—the twitches stack on top of each other. This is called wave summation.

• If the signals come very fast, the twitches blend into a strong, smooth, continuous contraction called tetanus

Rigor Mortis

muscle stiffens after death, speed depends on species

chicken 30-40 min

human, pig, cow: hours

deterioration of the SR, this releases all Calcium

lackof ATP production

this means that myosin cant effectivly release froma ctin so the tension stays high

how does Rigor Mortis end

degradation (enzymes break down myofilaments and other proteins) of myofilaments

muscle loses stiffness

part of why meat becomes tender as it ages

Energy for contraction and ATP (ATP PRODUCTION)

ATP provides the energy muscles need to contract, relax, and reset

generated 3 ways

• Direct phosphorylation

• anaerobic glycolysis

• aerobic respiration

Direct Phosphorylation (ATP PRODUCTION)

creatine phosphate transfers its phosphate to ADP to make ATP

15 seconds

fastest but only short time

1 phosphate : 1 ATP

Anaerobic Glycolysis (ATP PRODUCTION)

uses glucose and ATP to break it down to make ATP with no oxygen

1: 2 ratio

last 30-40 seconds

Aerobic Respiration (ATP PRODCUTION)

uses glucose,ADP, fatty acids, amino acids, and oxygen to produce ATP

about 1: 32-36 ATP

lasts hours

Muscle Types (colors)

red

white

pink

Red muscle

slow oxidative

uses lots of oxygen

needs capallaries

myoglobin and mitochondria

used in aerobic respiration atp production

red color from oxygen rich blood supply

White muscle

fast glycolysis

uses little oxygen

few capillaries, mitochondria and myoglobin

used in anaerobic glycolysis ATP production

Pink muscle

Mixed fibers, middle ground

oxidative and glycolytic

Skeletal issues

every species has some type

bird: bacterial chondronecrosis with osteomyelitis

• makes the bird lame

Skeletal system function

• support

• protect

• anchorage

• mineral and growth factor storage

• blood cell formation

• fat storage

• hormone production