BR Bio Set 1 Flashcards
types of glands
allows for secretion of substances into luminal space
Exocrine: secretion via duct
Endocrine: secretion via blood
neuromuscular junction pathway
As the action potential reaches the end of the axon, it triggers opening of calcium channels, causing synaptic vesicles to fuse w the pre-synaptic membrane for release of ACh into the synaptic cleft.
The released neurotransmitters diffuse through the synaptic cleft and bind to the post-synaptic membrane receptors, inducing conformational change of those receptors into a ligand-activated channel (ionophore) that is large enough to allow cations (such as Na+) to pass through
As cations enter the post-synaptic membrane, the muscle fibers depolarize and another action potential in the receiving neuron is eventually generated, thus allowing for propagation of the nerve signal
recycling in the neuromuscular junction
Calcium is recycled via endocytosis.
ACh, if left in the cleft, would continue to bind and allow cation diffusion, thus causing prolonged muscle spasms.
- To prevent this, an enzyme acetylcholinesterase (bound to the surface of the postsynaptic membrane) hydrolyzes acetylcholine into acetate and choline.
- These products are then recycled when they are transported back into the pre synaptic terminal, where they are used in the synthesis of acetylcholine.
excitatory v inhibitory postsynaptic potentials
E/IPSP
Whereas EPSP lead to an increase of the permeability of the postsynaptic membrane to positively charged ions, thus making depolarization more likely
vs. IPSP … negatively charged ions, thus making hyper-polarization more likely
cerebral cortex
- types of matter
- landmarks
Cerebral cortex: outermost layer of cerebrum
– Grey matter: nerve cell bodies and their dendrites
– White matter: myelinated axons of the nerve cells
Note: the matters are reversed in the case of the spinal cord
Landmarks of the cerebral cortex
- Central sulcus: prominent groove that separates the front lobes and parietal lobes
- Motor cortex: anterior to the sulcus; controls movement of individual muscles
- Sensory cortex: posterior to sulcus; detects sensations in various parts of the body via somatic receptors in the PNS
mono/polysynaptic reflex arc
eg. hammer impinging on the patellar tendon
As the hammer impinges on the patellar tendon, sensory neurons in the tendon become excited, sending impulses that travel along an axon to enter the spinal cord. They enter through the dorsal root ganglion and synapses with two neurons.
Monosynaptic reflex arc: One synapse is made to a motor neuron that immediately leaves the spinal cord and returns to the quadricep muscle, causing a contraction
– The quadriceps muscle is termed an extensor muscle because it extends (or straightens) the leg at the knee joint
Polysynaptic reflex arc: the other synapse is made to an interneuron that will, in turn, synapse with a different motor neuron that innervates the “hamstring” (bicep) in the back of the leg.
– The hamstring is termed a flexor muscle bc it bends (or flexes) at the knee joint
*** The contraction of one muscle inhibits the contraction of the other, THUS, in the patellar tendon example, only the monosynaptic reflex arc is followed through while the polysynaptic one is inhibited. This is observed as a smooth and coordinated movement at the knee joint where the lower portion o f the leg extends outwards.
What are the differences btwn the somatic and autonomic nervous system?
Somatic:
- Once nerve fibers leave CNS, they do not make a synapse until they have reached their effector organ
- At this organ, the neurotransmitter that is released is ACh
- Specifically, the CNS innervates the skeletal muscle
Autonomic:
- Once the nerve fibers leave the CNS, they synapse with a ganglion before making their final synapse with their effector organ
- —– Exception: adrenal medulla
- Only the preganglionic fibers release ACh; post will release norepinephrine
- Specifically, the ANS innervates glands, smooth muscle, and cardiac muscle
what is overlap in tactile discrimination and how does it affect our perception of the environment
Recall that the end of a neuron can be divided into many branches, which can in turn end at a receptor → these constitute a receptive field
- Depending on which area of the body, receptive fields are plentiful and can overlap – or there are very few, with no overlap
- Overlap means that we are stimulating more than one receptive field – which means we might feel that more than one area of the body is being stimulated when, really, it’s only a part of more than one receptive field.
LATERAL INHIBITION, mediated through interneurons within the spinal cord
- The axon that leads away from the field has lateral connections to interneurons that inhibit the impulses being sent down the axons from the other receptive fields
- Thus, only the appropriate signal will be sent to the brain for inference, rather than multiple
order of sensory neurons
There are FIRST-ORDER neurons carrying information from the receptive field(s) that enter the spinal cord and synapse with SECOND-ORDER neurons that ascent on the opposite side of the spinal cord to the thalamus. Then, another synapse is made with THIRD-ORDER neurons that continue to ascent until they reach a specific region of the somatosensory cortex for interpretation
The cerebral cortex itself contains cells that are organized into six horizontal layers
arteries
AWAY FROM THE HEART
durable because of the high pressure that comes with moving blood from the heart through the rest of the body → thus they have thick walls composed of both smooth muscle and connective tissue that contain both collagenous and elastic fibers
Elasticity prevents the blood pressure from becoming too high when it is ejected out of the heart but also maintains the high arterial pressure btwn the high systolic and diastolic phases of the heart → thus, allows blood flow to the rest of the circulatory system without sudden loss of pressure
capillaries
GAS EXCHANGE
Walls are composed of a unicellular layer of endothelial cells, surrounded by a basement membrane → thin layer allows for diffusion
Note: unlike the arteries, there is no connective tissue or smooth muscle
Capillary itself is just barely large enough for a red blood cell to squeeze through
Precapillary sphincter: regulates entry to the capillary bed; made of smooth muscle
veins
TOWARDS THE HEART
Due to the lowered BP in veins, the amount of smooth muscle and elastic tissue surrounding the veins is reduced → instead, veins use sympathetic nerves to control specialized valves
Specialized valves ensure blood flow happens in only one direction and prevent backward flow
– These valves can become damaged, thus allowing backward flow, thus increasing the pressure in veins → this damage is observed by the human eye as varicose veins, which are protrusions of the dilated veins beneath the skin
blood clotting
- factor X > II > XIII > vitK and Ca2+
the intrinsic and extrinsic pathways converge at factor X. Intrinsic factors are produced in the vessels, extrinsic factors are produced by the liver.
Factor Xa (the a just means activated) activates Factor II. Factor II is also called thrombin
Factor IIa converts fibrinogen to fibrin. Fibrin forms a weak clot by binding to a mass of platelets. Those platelets became stuck to each other because of thromboxane, ADP and serotonin that were produced upon vessel injury. So first develops a mass of platelets stuck to each other loosely. Then comes fibrin and forms a string around them–making a stronger, but still relatively weak clot.
Factor IIa also activates Factor XIII, which is a transglutaminase. Factor XIIIa links individual fibrin molecules together, making a strong clot.
Vitamin K is required to add an additional carboxylic acid to a glutamate residue on thrombin (and a few other factors). This makes that glutamate on thrombin have a negative 2 charge and allows it to bind Calcium ions.
The calcium ions complexed with thrombin are what allow the thrombin to stay near the plasma membrane. The plasma membrane is negatively charged, and the calcium is attracted to the membrane. This allows the clot to develop at the site where the vessel is broken. The breaks always occur on the edges of the vessels, so right where the epithelial plasma membranes are.
How does fat diffuse?
Fats are degraded into fatty acids and glycerol by lipases for diffusion into the intestinal epithelial cells
Once across the membrane, they resynthesize back into fats / triglycerides and aggregate into structures called chylomicrons
These aggregates or chylomicrons are released at the basolateral membrane and into the extracellular space, where they enter the lymph and are transported to the veins and eventually the tissues
kidneys
- nephron
- glomerulus
- bowman’s capsule
- blood plasma
- tubular structure
Functional unit of the kidney is the NEPHRON, consisting of the glomerulus (aka “little ball”), Bowman’s capsule, and a tubular system
Glomerulus: collection of capillaries that receive blood from an artery terminating in the renal system; hydrostatic pressure from the heart forces the blood to enter the Bowman’s capsule
Bowman’s capsule: contains a cell-free ultrafiltrate that lacks many of the plasma proteins found in the blood → basically, plasma minus the (large molecular weight) proteins
Blood plasma: 90% water + organic (ie proteins, sugars, amino acids, etc) + inorganic (ions) materials + red / white blood cells + platelets
Extending from BC is a long tubular structure which is divided into the proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT) and the collecting duct
