unit 3 bio

two types of cells in a neuron

neuron and glial cells

neurons

recquire 25% of oxygen

glial cells

servants of the nuerons, keeping them alive, force feeding them and protecting them

neurons are

eukaryotic cells characterized by having branches of membrane based appendages.

how are neurons characterized

dendrites and the axon

dendrites

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which conduct signals towards the cell body. They conduct graded potentials which is a little electrical signal based on levels of sodium and potassium.

The Axon

conducts an action potential. And is at the heart of how the nervous system works. Axon conducts the Ap away from the cell body.

what is the myelin sheath

a sheet called Myelin

what does the myelin sheath do

Myelin insulates the axon,The Schwann glial cells attach to the axon and travel around many times wrapping the m yelling sheet. This wrapping will increase the speed of action potentials. Myelinated axons increase from meters to hundreds of meters per second (100x faster).

white matter

Areas that have myelinated axons, does more communication because it sends signals very fast (a large part of the spinal cord)

Grey matter

without myelinated axons, does integration which does more critical thinking and memories. 

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what are the gaps in the myelin sheath ( the scwann cells)

nodes of raniver

\-Multiple sclerosis

 a loss in myelin, This leads to muscle contractile loss.

Action Potential

**the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.**

Resting potential

outside of the membrane we will have a high concentration of sodium ions. Which creates a positive charge outside the membrane. Inside we have a high concentration of potassium ions which has an overall negative charge due to the high number of negatively charged proteins (peripheral channels). This makes the membrane polarized as resting

Depolarization

Make the inside of the membrane more positive by bringing in sodium from the outside. To do this we use a voltage gated sodium channel- must be opened by a change in millivolts. A stimulation gets the line to threshold stimulation (10-15 mV stimulation) then it opens the channels and begin s to make the inside more positive very quickly exponentially.

Re-polarization

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makes the inside of the membrane less positive- At the peak, the voltage gated potassium channels open. This moves potassium out which just leaves negatively charged proteins and sodium ions behind. This decreases the positive charge and makes the inside more negative. 

We start an AP on the base of the axon, Why does it travel away from the cell body?

 Depolarization of a point causes the next second on the membrane to depolarize- this is self propagation.

what happens during the refractory period

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 you swap the ions so it blocks backward discharge of action potentials because of no gradient. 

Saltatory conduction

occurs at the nodes in myelin tube. The depolarization is so strong at the node that it will stimulate the next node to hit threshold stimulation. We do not have to do depolarization between nodes. With myelin we are cutting down the surface area with which we have to exchange ion

read over this on an action potential, maybe watch a couple youtube videos

AP goes to the terminal ends of the axon after it travels through and these ends have a little bulb at the end. This Axon terminal comes across from a muscle and creates a neuromuscular junction. This whole area of exchange of acetylcholine creates a synapse. Presynaptic membrane is on the axon terminal. The postsynaptic membrane is the one on the muscle. This space between the two membranes is the synaptic cleft. Sodium rushes in which causes depolarization in the axon terminal. We see a build up of vesicles…inside the vesicles will be a neurotransmitter. These vesicles come from the cell body where the Er and Golgi are. When the AP gets to the end of the bulb we see a voltage gated calcium channel. The voltage from the AP triggers the opening of this channel and we get an influx of calcium in the presynaptic axon. As the calcium rushes in, it triggers exocytosis because calcium is a necessity part of exocytosis. These vesicles are triggered to leave because calcium stimulates them. This then releases the neurotransmitter which flows into the synaptic cleft. These Neurotransmitters are ligands which bind to receptors on the postsynaptic membrane. When this binds to the receptor it cubes a channel to open. This is a ligand gated channel. This allows the sodium to flow from outside the muscle to inside. This is the depolarization of the postsynaptic membrane. 

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If the dendrite is depolarized by a connected synapse it depolarizes the cell body and moves all the way to the axon which causes the first sodium gated voltage channels to reach threshold stimulation and then Propagates from there. 

what happens at the neuromuscular junction

it is the area of exchange.

where is the presynaptic membrane

axon terminal

where is the post synaptic membrane

on the muscle

what causes depolarization in the axon terminal

sodium rushing in

what is the space between the synaptic membranes

the synaptic cleft

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what causes the voltage gated calcium channels to open

voltage from the ap

what happens when calcium rushes in

it triggers exocytosis

what do ligands do?

so ligands come from the calcium stimulating neurotransmitters to to be released, these are ligands. they bind to the receptors and it cubes a channel to open. this is a ligand gated channel

what can happen to extra acetylcholine?

it can be broken down by enzyme, or it can reuptake back into the presynaptic membrane. usually by endocytosis, sometimes it just diffuses out into the rest of the body.

what is the cns

brain and spinal chord.

peripheral nervous system

branching off of the cns, 12 pairs of cranial nerves, and 31 spinal nerves. this creates the 43 pairs of nerves here.

what is a nerve

an organ, (big collection of axon)

what is integration

the nervous system controlling movement through controlling contraction, also allows us to be conscious.

peripheral nervous

sends signals in and out of the cns to the rest of the body. it breaks into the sensory and motor divisions.

sensory receptors

nerve fibers

visceral

inside

somatic

outside

motor divison targets

muscles and glands

somatic nervous system

responsible for voluntary control. Secretes acetylcholine

cns targets

skeleton

autonomic nervous system

involved with involuntary control. Conducts impulses from CNS to cardiac muscles, smooth muscles, and glands.

two divisions of the autonomic nervous system

sympathetic and parasympathetic

sympathetic division

the fight or flight, mobilizes the body during emergency situations

parasympathetic division

conserves energy, promotes non emergency function. rest and demobilization. digestion and absorption goes up

read this

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Little clumps of cells, three weeks later it forms the primitive streak. The streak will get deeper and grow around the hole until it gets together and makes a tube. This is the neural tube. 4 weeks in we have the beginnings of the nervous system. If the circle does not close it causes spinal deformities. 

what are the 4 functional areas of the brain

cerebrum, cerebellum, diencephalon, and the brain stem

cerebellum

found hanging off the back of the brain. involves in coordinating muscle contractions. does this by sending signals to the cerebrum

diencephalon

little mass in the middle of the cerebrum has thalamus and hypothalamus

thalamus

relay station and routes information

hypothalamus

below the thalamus. controls temperature in the bodyo, feeding,

brain stem parts

midbrain, pons, and medulla

midbrain

functions in the head, noisem, and reflexes

pons

contributes to the medullas function

medulla

controls respirations and bp, cardiovascular and respiratory systems

action potentials

happen very quickly, doesnt last long.

the endocrine system is

very slow, when a gland stimulates its target, it can take minutes to see it happne, but it lasts a while

autocrine

to self

paracrine

to other cells in the tissue

in the endocrine system , our secreting cell

will be part of the gland, the stimulating ligand is now the hormone and that target cell is going to be somewhere else in the body.

to get continous stimulation, the nervous system

has to keep stimulating the target, due to the quickness of the ap

what do we use for the endocrine hormones to get to their targets

we use the blood

where do hormones get excreted

the urinary system

several hormones are

proteins!

steroid hormone

the first word means to resemble a cholesterol, because it is the startiung base reactant. aldosterone and cortisol are examples

amine hormonse

made from amino acid called tyrosine. they break into epinephrine and thyroxine

pituitary

There are many types of cells in the anterior, and as you move to the posterior there is a line where this stop and the posterior portion has not a lot of cells and barren strands. They function separately

anterior pituitary

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Looks to be separate from the infundibulum. Its job is to control other glands in the body, but it does not control its own functions. The hypothalamus controls it.

posterior pituitary

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Looks to be continuous with the infundibulum. Axons from the hypothalamus are extended into here. It truly is its part of the hypothalamus. Axons secrete neurotransmitters, but when in the blood they become hormones. 

what happens when the hypothalamus releases a release hormone

stimulates the anterior pituitary to release the tropic (stimulating) hormone. If it has the term releasing, it came from the hypothalamus, if it has the word tropic or stimulating, it came from the anterior pituitary.

thyroid gland

Thyroid hormone and and calcitonin

what is thyroid hormone though?

regulates metabolism…increases metabolic rate,

The thyroid hormone gives negative feedback

to the hypothalamus which inhibits the hypothalamus’s production of TRH.

Adrenocorticotropic hormone

stimulates the adrenal cortex

TSH

Stimulates the thyroid gland.

FSH and LH

gonadotropins- stimulates the gonads-testes and ovaries.

Melanocyte stimulating hormones (MSH)

allows for color change, but ours operate more autonomously.

Growth Hormones GH

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Makes you grow by targeting tissues and making them reproduce. If it is a tropic hormone from the ant. Pit, it stimulates the liver to make somatomedins which stimulates bone and muscle growth.

Prolactin

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is from the anterior pit. stimulates the mammary glands to produce milk.

Posterior Lobe

ADH (1st)

tells the uterus to contract through positive feedback.

Oxytocin (2nd)

Thyroid consists of

Follicle

what is follice

is filled with a protein-iodine based gel

Thyroid hormone is an

amine based hormone

Thyroxine= T4 (4 iodine)

 secretes from the gland and one iodine is removed when in the blood, which makes it T3

T3

is thyroid hormone

The sympathetic system has

nerves that run to the medulla that stimulates it to release

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Renal Cortex- 3 layers-

the three zonas-produces steroid hormones

Zona Fasciculata-

Gets stimulated by ACTH which leads to the production of cortisol- an anti-inflammatory, stimulates glucose sparing which is produced in between feeding periods. Body starts using fat and protein for energy and spares glucose for the brain.

Cortisol

stimulates hypothalamus which makes you feel hungry and irritable.

Zona Glomerularis

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1.  produces aldosterone. This zone is stimulated by angiotensin 2 and sodium

Zona Reticularis

produces androgens- sex hormone

The pancreas

Accessory to the digestive tract. Between stomach and small intestines. There is a duct that dumps things in the small intestine. This duct is in the pancreas, so it is an exocrine gland.

Pancreatic Islet

specialized packets of endocrine tissue- insulin and glucagon- function to regulate blood glucose levels

Insulin

lowers blood glucose

glucagon

elevates blood glucose

70-110 mg/dl

 homeostatic range

Beta cells in the islets

tart secreting insulin which is a humoral stimulus

There are three targets for insulin

muscle tissue, fat tissue, and the liver.  Insulin will cause these three targets to start absorbing glucose

In muscles

we use glucagon to produce ATP and store as glycogen