Midterm 2 combined

Load

A force exerted by a weight

Tension

opposing force from muscle contraction

slow oxidative

• aerobic, low power, fatigue resistant, sustained activity

• slow myosin ATPase + SERCA activity

• small diameter

• high capillary density

• high myoglobin content

• more prominent color if applicable

fast glycolytic characteristics

• anaerobic glycolysis, produce high power, rapid contractions, use low mitochondria, myoglobin, & capillaries

• prone to fatigue, ideal for short bursts of energy

• large diameter

• pale color if applicable

Muscle fatigue

inability to contract even when muscle is receiving stimulus

• muscle fiber starts fatigue when running low on ATP

Motor unit

single motor neuron and all the muscle fibers it innervates, which work together to produce muscle contractions

• each muscle fiber is innervated by only one neuron

• one motor neuron can innervate up to hundred of muscle fibers

• when one lower motor neuron fires, all the muscle fibers in a motor unit contract tg

• one muscle contains many motor units

Flexion

is the bending of the biceps

• flexors shorten

Extension

extension of the biceps

• extensors shorten

isometric contraction

builds tension in muscle, tension=load, first phase, lift & counterbalance weight

concentric contraction

muscle shortens, tension>load, second phase

eccentric contraction

muscle lengthens (generate tension while lengthening, elongating), tension<load, third phase

Factors affecting muscle tension

1. Number of motor units recruited

2. Frequency of stimulation of each motor unit

3. Resting sarcomere length before contraction

4. Size of muscle fibers in the motor units

How is motor unit recruitment used to regulate muscle tension?

regulates muscle tension by CNS, small, weaker motor units are activated first, then larger & stronger forces are added as force is needed

• more motor units being activated —> more tension

 how is action potential frequency used to regulate muscle tension

• If APs are far apart in time, there’s 2 separate twitches

• If APs are closer, second contraction begins before first relaxation finishes (temporal summation)

More motor units getting activate means …

more tension

Single muscle twitches

If the APs are far apart in time, we observe 2 diff twitches

Temporal summation

If the APs are closer, the second contraction begins before the first relaxation finishes

• contractions build open each other, refractory period is shorter than the time it takes the muscle to fully relax

unfused tetanus

if frequency is higher still, muscle reaches this steady state, allows muscle to maintain a constant tension, go back & forth btwn partial contraction & relaxation

Fused tetanus

if frequency is super high, muscles reaches this rly rare, no relaxation, rapid fatigue stage,

the larger the muscle fibers within a motor unit, the more _______________

tension they produce

Muscle fiber size influences tension by increasing _______________ and therefore the total ___________________

the number of sarcomeres & force-generating potential

how does the length-tension relationship and muscle fiber size influence the generation of muscle tension?

Optimal resting length is a maximum possible tension (peak)

Overly contracted: lower length in graph, little tension

Overly stretched: too loong, little tension

Autonomic Nervous system

• neurons that innervate our internal organs

• self-governing

many ANS organs are under antagonistic control by ….

sympathetic & parasympathetic divisions

Label (L to R)

preganglionic neuron, autonomic ganglion, postganglionic neuron, neuroeffector junction, effector organ (like smooth or cardiac muscle)

neuroeffector junction

synapse btwn postganglionic neuron & effector neuron

steps of neuroeffector junction function

1. Action potential arrives

2. Depolarization opens VG Ca2+ channels

3. Ca2+ triggers vesicle exocytosis

4. Neurotransmitter binds receptor

5. Neurotransmitter diffuses away after
   some time

6. Varicosity reuptakes neurotransmitter

7. Neurotransmitter is recycled for the future

Sympathetic and parasympathetic divisions differences

1. neurotransmitter used at each synapse
2. preganglionic neuron’s point of origin in the CNS
3. location of the autonomic ganglion

neurotransmitters and receptors involved in the sympathetic

preganglionic: acetylcholine & nicotinic receptor

postganglionic: norepinephrine & adrenergic receptor (ionotropic)

neurotransmitters and receptors involved in the parasympathetic

preganglionic: acetylcholine & nicotinic receptor

postganglionic: acetylcholine & muscarinic receptor (metabotropic)

vagus nerve

consists of 80% of a parasympathetic axons

part of vagus nerve that innervate upper body (above hip), originates from:

brain stem

part of vagus nerve that innervate lower body (hip & belod), originates from:

sacral region of spinal cord

part of sympathetic NS that innervate upper body (above hip level), originates from:

thoracic part of spinal cord

part of vagus nerve that innervate lower body (hip & below), originates from:

lumbar region of spinal cord

distance of sympathetic & parasympathetic to spinal cord

SNS: near, form sympathetic chain

PSNS: far, close to target organ

adrenal glands

where some preganglionic neurons synapse in & produce hormones that regulate various bodily functions

• consist of chromaffin cells (post ganglionic)

what type of control is the smooth muscle making up blood vessels under?

sympathetic control

3 subtypes of adrenergic receptors

1. alpha 1

2. beta 1

3. beta 2

bind E & NE

characteristics of alpha 1

expressed by: smooth muscle

promotes contraction

cause vasoconstriction, blood vessels tighten, increase bp, happens by catecholamines like NE & E

characteristics of beta 1

expressed by: cardiac muscle

promotes contraction

increase heart rate & contractility, increasing cardiac input & bp

characteristics of beta 2

expressed by: smooth muscle

promotes relaxation

causes vasodilation, widens blood vessels to increase blood flow to tissue

similarities & differences of smooth muscle and skeletal muscle in contraction

like: contraction is triggered by an increase in cytosolic Ca2+

unlike: no AP is required for contraction, Ca2+ comes from both SR & extracellular space, has less Ca2+ stored in SR

mechanisms where calcium can enter smooth muscle cells, explain

1. Hormone/NT pathway

   a. hormone/NT bind to GPCRs, GPCR activate second messenger, second messenger opens Ca2+ channels linked to G-protein pathways, —> Ca2+ entry

   b. hormone/NT bind to GPCRs, GPCR activate second messenger, second messenger opens Ca2+ channels in SR, —> Ca2+ release in cytosol (intracellular)

2. Mechanical Stretch Pathway

   • mechanical stretch opens mechanically gated Ca2+ channel —> Ca2+ entry

how does Ca2+ cause smooth muscle contraction

1. cytosolic Ca2+ concentration rises

2. Ca2+ binds calmodulin

3. Ca2+- calmodulin complex activate MLCK

4. MLCK phosphorylate myosin light chain (enhance ATPase activity, hydrolyze ATP), myosin & actin form cross-bridges

what does ATP hydrolysis do in muscle contraction

• Reset crossbridge cycle

• Energize myosin

Baseline ATPase activity is very low & must be enhance for contraction to occur

How does Ca2+ cause muscle relaxation

1. cytosolic Ca2+ concentrations falls

   • pumped out of cell

   • pumped into SR thru SERCA

2. Ca2+ unbind from calmodulin, MLCK inactivates

3. MLCP dephosphorylates myosin light chain

4. Myosin ATPase activity decreases, & myosin returns to an inactive state

balance between _____________ and _______________ activity is one of the main regulators of contraction

MLC kinase & MLC phosphatase

MLC kinase activity is enhanced by the ___________

Ca2+ calmodulin complex

MLC phosphatase activity is regulated by various ____________

G-protein-coupled pathways

Both alpha 1 & Beta 2 are …

GPCRs

more ca2+ will lead to ______ of myosin light chain

more, so much that it eventually caps off

more Ca2+ —> more phosphorylation —> more tension

how autonomic regulation through the alpha-1 adrenergic receptors influences smooth muscle contraction

1. PKC phosphorylates & opens Ca2+ channel (TRPC) —> Ca2+ entry

   • G protein pathway leads to opening of Ca2+ channels on membrane

2. SR binds IP3 gated Ca2+ channels —> Ca2+ release intracellu

how autonomic regulation through the beta-2 adrenergic receptors influences smooth muscle relaxation

1. PKA can phosphorylate SR & prevent binding to IP3

2. PKA activates MLCP

Characteristics of smooth muscle

contractile unit: actin & myosin

source for Ca2+ for contraction: extracellular fluid & SR

site of Ca2+ regulation: calmodulin in cytosol

branch of NS that regulate contraction: ANS

effect of stimulation by NS: contraction or relaxation

relative spd of contraction: slow

presence of gap junctions: yes, in some organs

Characteristic of Skeletal muscle

contractile unit: actin & myosin

source for Ca2+ for contraction: SR

site of Ca2+ regulation: troponin on thin filaments

branch of NS that regulate contraction: SNS

effect of stimulation by NS: contraction

relative spd of contraction: fast

presence of gap junctions: no

peptide/protein hormones

made of linked AA, large & hydrophilic

ex: insulin, glucagon, growth hormone, prolactin

steroid hormones

derived from cholesterol, small & hydrophobic

ex: cortisol, testosterone, estrogen, & progesterone

amine hormones

made of modified AA, small & hydrophobic/hydrophilic

ex: dopamine, epinephrine, norepinephrine, thyroid hormone

catecholamine: adrenal gland, more hydrophilic, cell surface

thyroid gland: thyroid gland, more hydrophobic, intracellular

Peptide hormones characteristics

Source: most glands (pituitary, pancreas, & parathyroid )

Synthesis & storage: Made in rough ER, post-translational modifications in Golgi, stored in vesicles

Transport: soluble in blood, degraded after a few mins by enzymes

Mechanism of action: Bind to cell-surface receptor, typically GPCRs

Steroid hormones characteristics

Source: adrenal glands, testes, & ovaries

Synthesis & storage: Made in smooth ER, diffuse out almost immediately

Transport: not soluble in blood, bound to protein carriers, shield hormone from degradative enzymes

Mechanism of action: Diffuse into cells & bind intracellular/ intranuclear receptors

exocrine gland

when contents are secreted into a duct

ex: sweat gland

hormone

chemical messengers secreted in bloodstream

nontropic hormone

hormone acts on peripheral target cells

tropic hormone

hormone that stimulate another endocrine gland to secrete its own hormone

hormones characteristics

endocrine system, hormones are released in body for general distribution, widespread effects, reacts more slowly, GPCRs or intracellular steroid receptors

neurotransmitters characteristics

nervous system, release NT at synapses onto specific target cells, local & specific effects, fast

endocrine gland

no duct needed, contents secrete directly to extracellular space

secrete hormones

ex: adrenal gland

Amine hormones characteristics

Source: adrenal & thyroid gland

Synthesis: Made in cytosol, from modifying AA like tyrosine

what part of the brain regulate hormone release?

hypothalamus

Simple endocrine reflex

endocrine cell (gland) directly senses a stimulus and responds by secreting a hormone, regulate hormone release, occur at the level of the gland

hypothalamus

main integrating center for hormone release, regulate

pituitary gland

regulates many of the organs of the body

anterior pituitary

linked to hypothalamus by blood vessels (portal system)

portal system

local blood vessel networks that connect 2 nearby structures

steps of hormone release in anterior pituitary

1. neurons in hypothalamus release hormones

2. hormones travel thru portal system to anterior pituitary

3. endocrine cells of anterior pituitary release their own hormones

posterior pituitary

axons from the hypothalamus extend directly into the
posterior pituitary

• not a true gland, dont have its own hormone producing cells

steps of hormone release in posterior pituitary

1. neurons in hypothalamus make hormones

2. hormones are stored in vesicles in axon terminal

3. neurons release hormones to rest of body

tropic hormones

act on glands and influence their hormone production

Non-tropic hormones released in pituitary gland directly exert effect on…

tissues of the body

ADH/vasopressin

nontropic, posterior pituitary hormone that affects osmolarity, water secretion

simple endocrine feedback loop

take place at the level of the gland

• substance being regulated is source of feedback

complex endocrine feedback loop

involve coordination by hypothalamus

• tropic, the downstream hormone is source of feedback

• nontropic, depends on specific hormone & specific effect achieved

adrenal gland medulla

synthesize epinephrine

adrenal gland cortex

synthesize cortisol

cardiovascular system 2 major divisions

systemic division & pulmonary division

pulmonary division

R side of heart pumps deoxygenated blood to the lungs for gas exchange & returns blood to heart

systemic division

L heart, pumps oxygenated blood thru aorta rest of the body and return blood in oxygen derived state

heart in cardiovasc system

central pump, w/ R & L sides working in parallel

blood vessels in cardiovasc system

tubes that carry blood

ex: arteries, veins, & capillaries

blood in cardiovasc system

fluid that transports oxygen, nutrients, hormones, & waste

valves

ensure unidirectional blood flow

fast oxidative glycolytic

• aerobic & anaerobic, intermediate, higher tension contraction, moderate fatigue resistant contractions, moderate intensity

• medium myosin ATPase + SERCA activity

• medium diameter

• medium capillary density

• medium myoglobin content

• more moderate color if applicable

arteries

carry blood from heart

aorta

largest artery

coronary artery

supply blood to heart muscle itself

vein

carry blood twds heart

vena cava

largest veins

vena cava splits into:

superior & inferior

each artery branches into many _________, which in turn branch into __________

arterioles & capillaries