Potential exam questions Flashcards
What is the advantage of fast uptake of Ca2+ in a skeletal muscle cell?
fast reuptake of calcium prevents the muscle from becoming fatigued.
When Ca2+ is allowed to remain in the cytoplasm, it will continue to bind to the troponin, causing tropomyosin to move away from the myosin binding-sites on actin and cross bridge formation will continue.
Describe the adaptations of the gulf
toadfish, what does this mean for muscle
contraction/relaxation?
The gulf toadfish has several adaptations which allow for the rapid contraction and relaxation of its swim bladder. When its swim bladder contracts, it generates a sound which can be used for mating purposes among others.
Adaptations:
Calcium:
-maximal density of Ca2+-ATPase pumps in SR
-exclusion of mitochondria
-high volume of SR (about 30% of muscle volume)
-different Ca2+ pump isoforms that release calcium at various rates
Myosin cross bridges:
-troponin isoforms with lower affinity for Ca2+ for rapid release of cross bridge binding and increased frequency of beats
-a lower proportion of cross bridges are attached at any given moment
-muscle strength is weak
This tells us that muscle strength needs to be weak in order to contract rapidly.
Compare how innervation is different between skeletal and smooth muscle
- both innervated by afferent and efferent neurons
- Skeletal muscle is innervated by the somatic nervous system (motor neurons), while smooth muscle is innervated by the autonomic nervous system.
- Most smooth muscle is dually innervated by the SNS/PNS. Smooth muscle in digestive organs is also innervated by the enteric nervous system.
Describe how a build up of tension occurs in both skeletal and smooth muscle
Smooth:
-tension in single-unit smooth muscle is modified by varying cytosolic Ca2+
-more Ca2+ leads to more cross bridges which leads to more tension
Skeletal:
-the greater the number of muscle fibers, the greater the amount of tension
-higher number of motor units recruited = higher tension
-higher number of muscle fibers per motor unit = higher tension
-larger muscle size = higher tension
-repetitive stimulation of a fiber can lead to higher tension and tetanus
-length of fiber at the onset of contraction (optimal length causes a favorable length-tension relationship) (not too stretched and not too constricted)
-extent of fatigue (fatigued muscle displays less tension over time)
-thickness of fiber (testosterone contributes to thickness)
Describe how BP is regulated
-NO is a vasodilator which helps to regulate BP
but more importantly…
Baroreceptor reflex:
-negative feedback system
-baroreceptors are STRETCH receptors which respond to CHANGING PRESSURE.
-located in carotid sinus and aortic arch
-INCREASED ARTERIAL BP WILL CAUSE INCREASED AFFERENT AP FREQUENCY FROM BARORECEPTORS
-neural signals sent to cardiovascular control center in the medulla
-This leads to decreased SNS activity; increased PNS activity
-This causes lower HR and stroke volume
-decreased C.O. and peripheral resistance
-DECREASED BP AS A CONSEQUENCE.
What are the forms and functions of the different blood vessels (arteries)
Arteries:
- thick
- large radii
- highly elastic walls
- allow for rapid transport of blood from heart to systemic organs
- act as a pressure reservoir to maintain constant flow of blood
What are the forms and functions of the different blood vessels (arterioles)
Arterioles: -not many elastic fibers -highly muscular -innervated by SNS -smaller radii Function: -direct blood to various systematic organs depending on their need -primary resistance vessels -regulate body-wide BP -intrinsic controls: local metabolic changes causing vasodilation/vasoconstriction (e.g., drecreased O2, increased acid, increased CO2, increased K+, increased osmolarity, release of adenosine, histamine causing increased bloodflow, temp changes) -extrinsic control: SNS influence, adrenal hormone influences, muscular activity, cardiovascular control center in brain, other hormones. -
What are the forms and functions of the different blood vessels (capillaries)
Capillaries:
- thin walled
- large cross-sectional area
- highly branched
Function:
- site of exchange
- determines the distribution of ECF between plasma and interstitial fluid
- ultrafiltration: pressure outside capillaries is less than pressure inside capillaries, allowing for fluid to be pushed out through pores
- reabsorption: pressure outside is greater than inside. Fluid moves back into capillaries
What are the forms and functions of the different blood vessels (veins)
Veins:
- thin-walled
- highly distensible (due to low elastic fibers but high collagen, STRETCHED BUT DOES NOT RECOIL)
- large radii
- high in collagen compared to other vessels
- contains valves which prevent backflow
function:
- serve as blood reservoir
- passage of blood back to heart
What law defines blood flow rates?
Hemodynamic flow law:
Q = delta P / R
Q - flow rate
delta P - Pressure 1 - Pressure 2 (pressure at the inflow end of the vessel - pressure at the outflow end)
R - Resistance of blood vessels
Follow a drop of blood through the right atrium and back again
- deoxygenated blood enters the right atrium through the superior vena cava
- blood flows through the right AV valve (tricuspid) into the right ventricle.
- from right ventricle, through pulmonary valve, into pulmonary artery and to the lungs.
- from lungs, now oxygenated blood enters the left atrium through the pulmonary vein
- from left atrium to left ventricle through the left AV valve (mitral).
- from left ventricle out to systematic circulation through aorta.
- arteries – arterioles – capilaries – venules – veins –superior vena cava – cycle repeats
For the following stimuli, what type
of receptor is involved: a) blood oxygen, b) acceleration, c) light
a) blood oxygen: chemoreceptors
b) acceleration: mechanoreceptors
c) light: photoreceptors
What are the three types of sensory receptors classified by role?
- interoceptor: detects info about the internal body fluids usually crucial to homeostasis, such as BP and O2 concentration.
- proprioceptor: sends information about movement and position of an animal’s body or certain parts such as limbs.
- exteroceptor: the senses which detect external stimuli such as light, chemicals, touch, temp, etc.
Explain how a stimulus triggers a response
- generator potential:
- a local depolarizing change when the sensor is itself a specialized afferent neuron.
- stimulus binds to stimulus-sensitive channel, causing the opening of nonspecific cation channels. This causes influx of Na+.
- depolarization results in the opening of voltage-gated Na+ channels, which bring in more Na+
- threshold is reached and AP self-propagates to CNS. - Receptor potential:
- local depolarization change when the receptor is a separate cell, closely associate with an afferent neuron.
- Stimulus binds to stimulus-specific channel, causing net influx of Na+.
- this results in the opening of voltage-gated Ca2+ channels and an influx of Ca2+
- Ca2+ triggers the release of NTs, which bind to chemically-gated channels on afferent neuron. Net influx of Na+.
- depolarization opens voltage gated Na+ channels in adjacent regions
- threshold achieved and AP self-propagates to CNS
Compare tonic and phasic receptors
Phasic receptors:
-adapt quickly
-respond to stimulus intensity
-decreased rate in APs over time, eventually disappear even with stimulus present
Tonic receptors:
-adapt slowly
-respond to absolute magnitude of stimulus
-Afferent APs persist until stimulus is removed
