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Largest most distinctive part of brain.
Allows reasoning and cognition
devoted to coordinating movement and balance
most nerve cells are here
process sensory info and coordinate the execution of movement
sensory input into this comes from somatic receptors in the periphery of the body and from receptors for equilibrium and balance located in inner ear
Also receives motor input from neurons in cerebrum
mostly myelinated axons and contains very few cell bodies
pale color comes from the myelin sheaths
roots right before nerve joins the spinal cord
dorsal: specialized to carry incoming sensory information
-dorsal root ganglia contain cell bodies of sensory neurons
ventral: carries info from the CNS to muscles and glands
ventral horns of grey matter contain cell bodies of motor neurons that carry efferent signals to muscles and glands and efferent fibers leave the spinal cord via the ventral root
oldest and most primitive region of the brain
some ascending tracts from the spinal cord pass through the brain stem and other ascending tracts synapse there
11 of 12 cranial nerves (carry motor and sensory info) originate along brain stem
a diffuse collection of neurons that extends throughout the brain stem
-many nuclei are associated with this
involved with arousal and sleep, muscle tone and stretch reflexes, coordination of breathing, blood pressure regulation, and modulation of pain
primary function is to act as a relay station for info transfer between the cerebellum and cerebrum
coordinates the control of breathing
structure formed by axons passing from one side of the brain to the other
this ensures the hemispheres communicate and cooperate
frontal: skeletal muscle movement
parietal: sensory info from skin, musculoskeletal system, viscera, and taste buds
-Subdivided into somatic motor neurons and autonomic neurons
-Carry info from CNS to muscles or glands
functions aren't under voluntary control
Divided into sympathetic and parasympathetic branches
dominant in stressful situations
fight or flight
body prepares for fight or flee and heart speeds up, blood vessels dilate, and liver produces glucose for energy for muscle contraction
-most pathways originate in the thoracic and etic lumbar regions
-sympathetic ganglia are found along vertebra
-short preganglionic neurons and long postganglionic neurons
control rest and digest functions
-pathways originate in brain stem and axons leave the brain in several cranial nerves
-para gang. are located either on or near their target organs
-pregang have neurons with long axons and postgang neurons have short axons
-sym and para pregang release ACh onto nicotinic cholinergic receptors on the postgang cell
-postgnag sym neurons secrete NE onto adrenergic receptors on the target cell
-most postgang para neurons secrete ACh onto muscarinic cholingergic receptors on target cells
smooth muscle, cardiac muscle, exocrine glands, few endocrine glands, lymphoid tissues, and some adipose tissue
synapse between a postgang auto and its target cell is neuroeffector junction
-axons end with a series of swollen areas which are filled with neurotransmitter. Neurotrans is released into interstitial to diffuse to where receptors are...means it can affect a large area of target tissue
when an action potential arrives, voltage-gated Ca channels open and it enters the neuron and the synaptic vesicle are released by exocytosis. Once neurotransmitter is released into synapse, they either diffuse through the interstitial fluid until they encounter a receptor or drift away from synapse
-more neurotrans. means longer or strong response
Receptors found in skin and viscera
Receptor activation triggers a-potentials
Neurons with nociception, temp, and coarse touch synapse onto secondary neurons shortly after entering spinal cord to brain. Fine touch, vibration, and proprioceptive neurons have long axons that go up spinal cord to medulla
part of brain that recognizes where ascending sensory tracts originate.
more sensitive a region of body is to touch, the bigger the corresponding region in the cortex and if body part is used more, the region will expand in cortex
Physical contact, stretch, steady pressure, movement, vibration and texture
composed of nerve endings surrounded by connective tissue which create large receptive fields. Responds to high-frequency vibrations that opens mechanically gated ion channels. Adaptive: respond to change then ignore (shirt)
Free nerve endings
Cold and warm receptors and thermoreceptors are important in this process
Receptive field is about 1mm. more cold than warm with a range of 20-40 celcius
Thermorecpetors use cation channels called transient receptor potential (TRP)
respond to strong chem, mech, or thermal stimuli that cause or have potential to cause tissue damage
Initiates adapative, protective responses like moving hand from oven
Also in muscles not just skin, like overuse
Activated by local chem that are released upon tissue injury
Pathways: reflexive response at spinal cord or ascending pathways to cerebral cortex that become conscious sensation (pain or itch)
free nerve endings whose ion channels are sensitive
carried to CNA
fast pain: rapidly transmitted by myelnated a-delta fibers (first stabbing sensation when stub toe)
Slow pain: duller and more diffuses and carried on unmyelinated C fibers (dull throbbing pain)
At resting phase (flat line)
Slow voltage gated K+ leak channels open.
K+ leaves cell.
During depolarization: Fast voltage gated Na+ channels open and sodium comes in and causes a rapid depolarization.
At the plateau: Fast voltage gated Na+ channels inactivate (not depolarizing anymore) so we see a small decline in potential.
But then we get this plateau! Because slow L-type Ca2+ channels are opening, so the depolarization extends.
During repolarization: Calcium channels close and slow voltage gated K+ channels open.
Potassium leaves cell, so membrane potential is going to repolarize and return to rest.
A long refractory period allows ventricles sufficient time to eject blood and refill before the next contraction.
Sodium channels inactivate and can only be reset through repolarization. If we add the calcium current and extend the duration of the action potential we also extend the duration of the refractory period.
If the refractory period is about as long as the twitch it means the muscle can relax before we activate it again.
This means that ventricular muscle can't undergo tetany. We want to pump the blood/fill the blood - we don't want a tetanic contraction. We don't want a long sustained reaction because our heart is a pump! It can't fill or contract for long periods of time.
Contractility increases when HR/Contractility/Preload increase.
HR = Faster cyclist pedals, faster he'll go.
Contractility = If cyclist flexes his muscles and pushes harder on pedals, bicycle will move faster.
Preload = Tailwind pushes biker, he'll go faster.
CO decreases when afterload increases.
Cycling against wind will slow him down.
OTHER EXAMPLES OF HOW ALL THESE THINGS AFFECT EACH OTHER:
1. Aldosterone secretion would increase plasma volume and primarily increase preload.
It would also increase blood pressure and therefore increase after load.
The main outcome is that SV would increase via a preload effect.
2. Atherosclerosis would increase afterload and has the potential to decrease the SV.
3. Blood transfusion would increase plasma volume, venous return and preload.
4. Increased extracellular calcium would increase contractility and stroke volume.
There could be an increase in vasoconstriction and afterload. The primary effect is
5. IV fluids would increase plasma volume, venous return and preload and therefore SV.
6. Sympathetic stimulation would increase contractility and blood pressure. The overall
effect would be to increase SV. But could also increase afterload.
7. Systemic hypertension would increase afterload.
8. Up regulation of beta adrenoreceptors by thyroid hormone would increase contractility and increase SV.
What it means to increase contractility: the ventricles will be stiffer at the end systole because they can contract more forcefully, so more blood can be ejected, so the ejection fraction increases, implies that afterload is decreased.
Remember: if stroke volume stays the same but afterload increases, the ventricles are working too hard. This is known as hypertension.
Remember: hypertension is when the stroke volume stays the same but afterload increases. The ventricles are working too hard and it is not healthy.
Compliance - change in volume/change in pressure
Fluid is put in veins because they are so compliant.
Elastic recoil - ability of vessel to return to original shape after a stretch.
If vessels didn't spring back, BP would drop, but the arteries spring back on the blood during diastole which maintains a pressure on the blood and the blood can keep flowing.
Pump of ventricle is on/off flow, but the elastic recoil of the arteries converts that to a continuos flow.
You can feel the pulse in your arteries.
STEPS TO HELP ME UNDERSTAND THIS
1. Ventricle contracts
2. Contraction of that ventricle opens the semilunar valve and ejects blood into the aorta and the aorta stretches out.
3. Aorta and arteries expand and store pressure in elastic walls.
4. Once the ventricle relaxes the semilunar valve closes, preventing flow back into the ventricle.
5. The aorta is just like a rubber band, it is stretched out and when systole is over we let go of the rubber band, and it springs back and recoils/pushes back on the blood, which generates a pressure gradient that keeps the blood flowing even though the ventricle is no longer contracting.
BLOOD IS PULSATILE.
What is mean arteriole pressure:
AVERAGE BLOOD PRESSURE IN INDIVIDUAL.
Average arterial pressure during single cardiac cycle.
Assuming BP= 120/70
70+(⅓)(120-70)= 87 mmHg
Blood will flow along path of least resistance. Arterioles have to take turns because we don’t have enough blood to maintain blood pressure.
Arteriolar resistance is influenced by both local and systemic control mechanisms.
There are two local factors that regulate blood flow.
1. Active hyperemia: matches blood flow to an increased metabolism. So it needs to meet metabolism needs, so the arterial dilates to increase blood flow.
Tissue/organ works harder→ release dilators→ arterioles dilate→ vascular resistance goes down→ blood flow goes up!
Reactive hyperemia: blood flow is occluded for a moment→ vasodilators accumulate→ arterioles dilate→ the occlusion is removed→ resistance decreases→ blood flow increases→ vasodilators actually wash away, and arterioles constrict again and blood flow returns to normal.
2. Autoregulation: keeps blood flow constant. Even though pressure is fluctuating, vascular resistance is adjusted so that blood flow will stay constant (especially in the kidneys/brain).
Macula densa is a chemoreceptor.
If there is too much flow or too much NaCl deliverythere is more work to do than the distal tubule can handle
That means the GFR is too high.
The Macula densa sends a chemical signal to constrict the AA so the GFR is brought down to level that is better for homeostasis
This is negative feedback.
What should be the intrinsic myogenic response if MAP were to decrease?
What would this response do to the GFR?
The GFR is the means by which the kidney cleans the blood. Plasma is filtered.. The useful substances are reabsorbed and the wastes are secreted and excreted...
If the GFR is too low, the blood is not being cleaned and wastes will start building up in your blood.
It's important that the GFR is high enough to maintain homeostasis and clean your blood.
BUT if the GFR is too high, the tubules are not able to process the filtrate .... Valuable water and electrolytes could be lost in the urine... this would be a threat to blood pressure maintenance.
Atrial natriuretic peptide dilates AA - ^ GFR
too much fluid, BP too high, need to get rid of some.
Blood pressure low due to hypotension or dehydration ↓ GFR so that we don't lose valuable fluid and our BP doesn't tank.
Constriction of Mesangial cells – ↓ GFR
Sympathetic stimulation - ↓ GFR until BP can be returned to normal
Constrict afferent arteriole and decrease GFR while we try to maintain our BP.
Angiogensin II is a vasoconstrictor – ↓ GFR until BP can be returned to normal
Na+: Crosses luminal side via secondary active transport with amino acids and crosses basolateral side via Na/K ATPase (secondary active transport
Glucose: Crosses luminal side via secondary active transport with Na+ and crosses basolateral side via facilitated diffusion transporter
Amino acids: luminal side via secondary active transport with Na+ and basolateral side facilitated diffusion transporter
Water: VIA OSMOSIS!!
The iso-osmotic reabsorption that occurs in the proximal tubule is due to the gradient that is created because of the Na/K ATPase. When the gradient is created, the Na will cross the luminal side of the cell and water will cross those sides via osmosis because there are lots of aquaporins in these epithelial cells.
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