353 exam 2

dual innervation

most organs receive input from sympathetic and parasympathetic systems

antagonistic action

one system stimulates while the other inhibits

basal tone

Even under resting conditions autonomic neurons carry APs

Pathway of ANS

autonomic nerve pathway consists of a two-neuron chain: preganglionic neuron, synapse, postganglionic neuron

preganglionic neuron

synapses with the cell body of the postganglionic fiber in a ganglion outside the CNS

postganglionic neuron

sends axons that end on the effector organ

Similarities of SNS and PNS

pathways contain two neurons in series (post/pre ganglionic neurons) ,pre/post ganglionic neurons synapse with each other in the autonomic ganglia

Differences of SNS and PNS

location of preganglionic cell boy

* SNS in thoracic and lumbar
* PNS in hindbrain and sacral
* location of ganglia
* SNS chain runs close to spine
* PNS close to effector organs
* number of postganglionic neurons that synapse with a single preganglionic neuron
* SNS ten or more
* PNS three or fewer

PNS postganglionic fibers release

acetylcholine via cholinergic fibers (nicotinic and muscarinic receptors)

SNS postganglionic fibers release

norepinephrine via adrenergic fibers (alpha and beta receptors)

PNS Target organs

NT = Ach receptor on target = cholinergic muscarinic

SNS target organs

NT = NE receptor on target = adrenergic (alpha 1/2, beta 1/2)

Ganglia of both PNS and SN

NT: Ach Receptor on post-ganglionic cell = cholinergic nicotinic

Divisions of the autonomic nervous systems are usually \________

reciprocally controlled (increase in one corresponds with decrease in another)

The adrenal medulla is a modified part of the

sympathetic NS

Effects of autonomic NS on the heart

Effects on heart: heart rate, stroke volume , results in increased or decreased cardiac output

Effects on vessels:

diameter change

blood flow and peripheral resistance

adrenal medulla

collection of modified postganglionic neurons that secrete epinephrine into the blood stream

Purpose of the adrenal medulla

* endocrine arm of the SNS
* integrated (vertebrate) stress response
* fight or flight response

effectors that receive only sympathetic innervation

sweat glands, erector pili muscles in the skin, kidneys, most blood vessels, adrenal medulla

two endocrines structures of the adrenal medulla

cortex (HPA axis) and medulla (SNS

adrenal medulla secretes

catecholamine hormones on stimulation by sympathetic input

SNS/endocrine response pathway

fast activation

hypothalamus = adrenal medulla

endocrine pathway

slower activation

hypothalamus - pituitary -adrenal cortex

what are endocrine calls in the adrenal medulla

modified post-synaptic neurons of the SNS that synthesize and secrete E into the blood

Effects of catecholamines

* increased cardiac output via increased HR and stroke volume
* increased blood flow to skeletal muscles
* reduced blood flow to internal organs
* increased ventilation (lungs)
* increased alertness (brain)
* relaxation of GI tract muscles
* elevated blood glucose concentrations

By control muscles:

skeletal and smooth

cardiac

By appearance/structure

striated and smooth

By energy source

red muscle

white muscle

fast and slow twitch

neurogenic (skeletal m)

needs nervous input via motor neurons

1AP from motor neuron =1 ap from muscle cell = 1 contraction

striated muscle

interaction proteins (thick and thin filaments) arranged into sarcomeres

the cross-bridge cycling \=

sequence of power strokes

motor unit

a motor neuron plus all its muscle cells

motor unit make up

,single motor nerve plus all innervated muscle fibers (myocytes) linear increase in contraction force with number of recruited motor units

subtypes vary in contraction speed rate of rise force,time to pea of twitch

thick filaments

polymers of myosin

thin filaments

polymers of alpha-actin

think and thin filaments form

myofibrils in myocyte

control proteins

troponin and tropomyosin regulate interaction between think/thin filaments

what do troponin and tropomyosin associate with?

actin, to regulate the availability of binding sites for cross bridge

sacromere

basic functional unit of striated muscle repeated in parallel and in serial arrangements in myocyte

excitation-contraction coupling \=

the conversion of APs into molecular interaction of filaments

APs from NMJ travel down \_____ \______ to release \_____ from SR into cytosol

transverse tubules and ca2+

Ca 2+ binds to \_____ to expose binding sites on \_______ for myosin cross-bridge

troponin and actin

Powerstroke pathway

1 binding: myosin cross bridge binds to actin molecule

2 power stroke : cross bridge bends pulling thin myofiliments inward

3 detachment : cross- bridge detaches at end of power stroke and returns to original conformation

4 binding: cross-bridge binds to distal actin molecule cycle repeats

properties of skeletal muscle contraction

length-tension relationship

twitch fusion tetanus

energy supply and fatiigue

tension\= function of \# cross-bridges \=

overlap of filaments

number of fibers contracting depends on

number of motor unites recruited

number of muscle fibers per motor unit

number of muscle fibers available to contract

tension developed by each contracting fiber cell depends on

frequency of stimulation

length of fiber at onset of contraction

extent of fatigue

type of fiber

thickness of fiber

What are reasons for muscle fibers to adapt

* improvement in oxidative capacity
* muscle hypertrophy = more filaments in myocytes
* influence anabolic steroids
* interconvention between fast muscle types
* muscle atropy
* limited repair of muscle

What causes fatigue?

lactic acid accumulation

inadequate glucose supply

ca accumulation outside sr

hypoxia

overheating

alternative pathways that muscle fibers use to form ATP

oxidative phosphorylation and glycolysis

creatine phosphate

Three types of skeletal muscle fibers

slow oxidative, fast oxidative, fast glycolytic

slow oxidative

long aerobic activity, slow long running

fast oxidative

long aerobic activity, swimming

fast glycolytic

short powerful movement, sprinting

where is smooth muscle found

wall of tubes in the body

\________ exerts pressure on and regulates forward movement of content of these structures

contraction

smooth muscle has \_______ and \_________ but not in myofibril arrangement

think and thin filaments with a sliding filament mechanism

cellular structure of smooth muscle cell

thick and thin filaments

dense bodies

microfilaments

adhesion plaques

smooth muscle cells contract in \_______________ \_____________

all dimensions

smooth muscle differences from skeletal muscle

no sacromeres

thick/thin filaments scattered in cell

thin filaments attached to: cell membranse adhesion plaques

dense bodies

cell can contract in all dimensions

no t-tubles and minimal SR

CA 2+ from extracellular sourcescells often connected by gap junctions

functions as a single unit

different mechaniism of excitation/ contraction coupling

no troponin/ tropomyosin

smooth muscle is regulated by

nervous input , hormones , mechanical forces and stretch

cell stimulation increased intracellular \__________

Calcium

Pathway of Ca2+ in smooth muscle

Ca binds to calmodulin

calamoudin causes phosphorylation of myosin

permits binding with actin (myosin ATPase activity)

cross binding cycling can occur

cardiac muscle

triated: sarcomeres with troponin and tropomyosin
lots of mitochondria
1 capillary per myocardial fiber
uninucleate
T-tubules
Ca from SR and extracellular fluid
gap junctions
desmosomes
intercalated discs contain two types of membrane junctions
1 mechanical

intercalated discs contain two types of membrane junctions 1 mechanical

2 electrical 2 mechanical

mechanical:

desmosomes hold cardiac cells together

electrical:

gap junctions link cells of each chamber into a functional syncytium

cardiac ventricular cell AP

1. resting potential
2. resting potential

3. slight repolarization 4. plateau phase 5. depolarization

what presents tetanus

long refractory period of cardiac ventricle cells

automaticity

the heart contract rhythmically as a result of APs that generates by itself (myogenic)

auto rhythmic cells

initiate and conduct the AP responsible for contraction of working cells

* called cardiac pacemaker cells
* located in certain areas (nodes and bundles)

where are cardiac pacemaker cells located

sinoatrial node

atroventricular node

bundle of His

what are the electrical conduction pathways

* purkinje fibers
* inter-atrial pathway
* electrical coupling of cells via gap junction

\

how to increase heart rate

NE released from sympathetic neurons and E released from the adrenal medulla

* more Na and Ca channels open
* rate of depolarization and frequency of APs increase

how to decrease heart rate

* ACh released from parasympathetic neurons
* more K channels open
* pacemaker cells hyperpolarize
* time for depolarization takes longer, frequency of AP decreased

end-diastolic volume

volume of blood in a ventricle at the end of relaxation

end-systolic volume

volume of blood in a ventricle at the end of contraction

stroke volume

volume of blood ejected from a ventricle per contraction

cardiac output

volume of blood pumped per minute

SV\=

end-diastolic volume- end-systolic volume

Frank-Starling relationship

\-depends on ventricular contraction force which is a function of the end-diastolic volume

* ultimate related to the length of sarcomeres in cardiac ventricular fibers similar to skeletal muscle

pathway of sympathetic activation

\-NE

adrenal secreated e

increased EDV by constricting veins (increased pressure)> increased venous return to the heart>greater stretch (intrinsic effect)

Cardiac output\=

heart rate x stroke volume

baroreceptors are found in the

aorta and carotid arteries

baroreceptors...

monitor blood pressure and relay information to cardiovascular control center

\______ blood flow through pulmonary and system loop

serial

\_______ blood flow through the organs in systemic circulation

parallel

Blood pressure in vasculature from high to low

left ventricle\> arteries (systolic higher than diastolic)\> arterioles\> capillaries\> venules and veins

What has the highest surface area and lowest pressure

capillaries, venules, veins

Peuseuille's Law

Flow rate \= (pi x change in pressure x vessel radius^4)/ (8 x blood viscosity x vessel length)

total peripheral resistance

overall resistance to blood flow from aorta back to the heart (vena cava to right atrium)

mostly at level of arterioles

mean arterial pressure

MAP \= diastolic pressure + 1/3 systolic pressure

Flow\=

MAP/R or MAP/TPR

What determines that diameter of the arterioles

smooth muscles surrounding them

myogenic activity of...

arteriolar and precapillary sphincters (local regulation)

* regulated by pressure-receptors of smooth muscle
* adjusts perfusion to changes in MAP

types of local chemical signals

* increase in adenosine, CO2, H+, K+ due to high tissue metabolism results in vasodilation
* adjusts perfusion to oxygen consumption
* histamine from mast cells (inflammation)- enhanced perfusion
* nitric oxide, vasodilator from endothelial cells

external regulation (of blood flow)

* nervous input and hormones \n NE (sym. NS, synapse) and E (adrenal glands)

capillary beds

sites of exchange/diffusion between blood and tissue