animal control systems Flashcards
Hormone
in multicellular organisms, one of many types of SECRETED CHEMICALS, that are formed in specialized cells, TRAVEL in body fluids, & ACT on specific target cells’ functioning
- are thus important in long-distance signalling
Steroid
a type of LIPID characterized by a CARBON skeleton consisting of 4 fused rings with various CHEMICAL GROUPS attached
Autocrine system
- when a cell is signally itself (in the nearby vacinity where a cell can shut down or limit its own ability)
and/or - when a cell is signally cells that are communicating with nearby cells of the same type
Paracrine system
like the endocrine system but on a SMALLER level, only cells LISTENING for it NEAR BY can receive it (have a RECEPTOR for it)
- like a smaller radio station
Endocrine system
some gland in body will broadcast signal to every cell BUT only the cells that are LISTENING for it receive it (have to have RECEPTOR for it)
Neuroendocrine
are cells that receive neuronal input (neurotransmitters released by nerve cells or neurosecretory cells) and, as a consequence of this input, release message molecules (hormones) into the blood. … Hormonal effects can last up to ten times longer than those of neurotransmitters.
Neurohormone
a molecule that is SECRETED BY A NEURON, travels in body fluids, & acts on specific target cells, changing their functioning
Receptor
are chemical structures, composed of protein, that RECEIVE and TRANSDUCE signals that may be integrated into biological systems.
Signal transduction
the CONVERSION of STIMULUS ENERGY to a CHANGE IN THE MEMBRANE POTENTIAL of a SENSORY RECEPTOR CELL
Negative Feedback
for many hormones, the response pathway involves NFB:
- a loop in which the response REDUCES the initial stimulus
- AMPLIFIES both stimulus & response
Positive Feedback
REINFORCES a stimulus, leading to an even greater response
- helps RESTORE a preexisting state
Homeostasis
the steady-state physiology condition of the body
Tropic hormone
a hormone that has an ENDOCRINE GLAND or CELLS as a target
Nontropic hormone
are hormones that DIRECTLY stimulate TARGET CELLS to induce effects.
Hormone cascade
1 hormone triggers the production of another hormone, that triggers the production of another hormone
Parathyroid hormone (PTH)
a hormone secreted by the parathyroid glands that raises blood calcium level by promoting calcium release from bone & calcium retention by the kidneys
Oxytocin
a hormone PRODUCED by the HYPOTHALAMUS & RELEASED from the POSTERIOR pituitary
- it induces contractions of the uterine muscles during labour & causes the mammary glands to eject milk during nursing
Insulin
a hormone secreted by pancreatic beta cells that lowers blood glucose levels
- it promotes the uptake of glucose by most body cells & the synthesis & storage of glycogen in the liver & also stimulates protein & fat synthesis
Glucagon
a hormone secreted by pancreatic alpha cells that raises blood glucose levels
- it promotes glycogen breakdown & release of glucose by the liver
Neuron
an impulse-conducting cell in the nervous system
- excitable
- processes input produces output
Sensory Neuron
any neuron that detects a stimulus & communicates it to the nervous system
Interneuron
any neuron that connects 2 other neurons
Motor Neuron
a nerve cell that transmits signals from the brain or spinal cord to muscles or glands
Soma
cell body
Dendrites
input end
- bunch of RECEPTOR molecules on it that detect some kind of input
- sensory receptors for the cell itself, either receive info from ANOTHER NEURON or info from a SENSORY CELL
Axon hillcock
where voltage is summed (& axon potential may or may not form) & sent down axon
The axon hillock acts as something of a manager, summing the total inhibitory and excitatory signals. If the sum of these signals exceeds a certain threshold, the action potential will be triggered and an electrical signal will then be transmitted down the axon away from the cell body.
Axon
a typically LONG extension, or process, of a neuron that carries nerve impulses AWAY from the cell body TOWARD TARGET CELL
- is insulated with myelin sheath
Ion pumps
a transporter is a transmembrane protein that moves ions across a membrane to accomplish many different functions including, cellular communication, maintaining homeostasis, energy production, etc.
Ion channels
a transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient
Gated ion channels
- changes in the membrane potential occur b/c neurons contain these
- ion channels that open or close in response to stimuli
Resting membrane potential
the membrane of an INactive neuron - one that is NOT sending a signal
- (-60mv–80mv)
is the voltage across the cell’s membrane when it is at rest (i.e. there’s no graded potential or action potential going on)
- it depends on ALL the equilibrium potentials for all the ions present
Threshold
the potential that an excitable cell membrane must reach for an action potential to be initiated
Action Potential
an action potential is the signal that neurons produce & send
- typically, they are formed when enough Na+ channels open
- different events open these channels on different neurons
- if a depolarization shifts the membrane potential sufficiently, the result is a massive change in membrane voltage (an action potential)
Depolarization
a change in a cell’s membrane potential such that the inside of the membrane is made less negative relative to the outside
EX: a neuron membrane is depolarized if a stimulus decreases its voltage from the RMP (70mV) in the direction of zero voltage
Repolarization
refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value.
Hyperpolarization
a change in a cell’s membrane potential such that the inside of the membrane becomes more negative relative to the outside
- reduces the chance that a neuron will transmit a nerve impulse
Refractory
the “down time” when a 2nd action potential cannot be initiated
Schwann cells
a type of GLIAL CELL that forms insulating myelin sheath around the axons of neurons in the PNS
Myelin sheath
wrapped around the axons of a neuron, an insulating coat of membrane from Schwann cells or oligodendrocytes
- it is interrupted by nodes of Ranvier, where action potentials are generated
Saltatory conduction
rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of ranvier to another, skipping the myelin-sheathed regions of membrane
Presynaptic cell
The cell that delivers the signal to the synapse
Postsynaptic cell
The cell that will receive the signal once it crosses the synapse
Neurotransmitter definition
a molecule that is released from the synaptic terminal of a neuron at a CHEMICAL synapse, diffuses across the synaptic cleft, & binds to the POSTsynaptic cell, triggering a response
EPSP (excitatory postsynaptic potential)
an electrical charge (DEpolarization) in the membrane of a postsynaptic cell caused by binding of an excitatory neurotransmitter from a presynaptic cell to a postsynaptic receptor; makes it more likely for a postsynaptic cell to generate an action potential
IPSP (inhibitory postsynaptic potential)
an electrical charge (HYPERpolarization) in the membrane of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from the presynaptic cell to a postsynaptic receptor; makes it more difficult for a postsynaptic neuron to generate an action
Temporal summation
a phenomenon of neural integration in which the membrane potential of the postsynaptic cell in a chemical synapse is determined by the combined effect of EPSPs or IPSPs produced in rapid succession
Spatial summation
a phenomenon of neural integration in which the membrane potential of the postsynaptic cell is determined by the combined effect of EPSPs or IPSPs produced nearly simultaneously by different synapses
Cephalization
the concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain, both during evolution and in the course of an embryo’s development.
Ganglion/Brain
- clusters (functional groups) of nerve cell bodies in a centralized nervous system
- organ of the CNS where info is processed & integrated
- in more complex animals
Nerve
a fibre composed primarily of the bundled axons of PNS neurons
Nerve net
a weblike system of neurons, characteristic of radially symmetrical animals, such as hydra
Integration
Stimuli that are received by sensory structures are communicated to the nervous system where that information is processed. This is called integration. Stimuli are compared with, or integrated with, other stimuli, memories of previous stimuli, or the state of a person at a particular time.
Define tropic and non-tropic hormones
Non-tropic hormones are hormones that directly stimulate target cells to induce effects. This differs from the tropic hormones, which act on another endocrine gland. Non-tropic hormones are those that act directly on targeted tissues or cells, and not on other endocrine gland to stimulate release of other hormones.
Compare the basic structure of sensory neurons, interneurons, and motor neurons
sensory neurons: transmit info about external stimuli such as light, touch, or smell, or internal conditions such as blood pressure or muscle tension
interneurons: the vast majority of neurons in the brain are interneurons, which form the local circuits connecting neurons in the brain
motor neurons: neurons that extend out of the processing centres trigger output in the form of muscle or gland activity
- ex: transmit signals to muscle cells, causing them to contract
Explain what an excitable cell is
meaning their voltages can change
- neuron & muscle cells are “excitable”
Compare ion pumps and ion channels
ion pumps: a transporter is a transmembrane protein that moves ions across a membrane to accomplish many different functions including, cellular communication, maintaining homeostasis, energy production, etc.
ion channels: a transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient
Discriminate between the three types of ion channels
voltage-gated ion channels open with changes in the membrane potential; ligand gated channels open in response to changes in the concentration of specific signalling molecules; stretch-activated ion channels open in response to changes in cell shape
Explain how action potentials are first generated in neurones
The action potential is an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. … Action potentials are caused when different ions cross the neuron membrane. A stimulus first causes sodium channels to open.
Describe the purpose and mechanism of refractory period
- the “down time” when a 2nd action potential cannot be initiated
- this interval sets a limit on the max frequency at which action potentials can be generated
- also ensures that all signals in an axon travel in 1 direction, from the cell body to the axon terminal
Compare a postsynaptic cell’s responses to excitatory and inhibitory neurotransmitters
if acetylcholine (ACh) binds to an EXCITATORY receptor, it might open Na+ channels on postsynaptic cells - this RAISES the neurons voltage TOWARD threshold
if ACh binds to an INHIBITORY receptor, it might open K+ or Cl- channels
- this LOWERS the neuron’s voltage, making it HARDER to fire
Explain how the central nervous system integrates sensory information and elicits a motor response
- sensory receptor (of some kind)
- sensory input (brought into the black box (brain) - PNS doing connection)
- integration
- motor output - PNS doing connection
- effector cells
*PNS connects the outside world to CNS
Explain the mechanism and purpose of the withdrawal reflex
The withdrawal reflex is a spinal reflex intended to protect the body from damaging stimuli. The reflex rapidly coordinates the contractions of all the flexor muscles and the relaxations of the extensors in that limb causing sudden withdrawal from the potentially damaging stimulus.
Nervous system
has to be a DIRECT LINE in order for 2 cells to communicate (like a telephone)
- opposite of endocrine system
What are the 2 broad classes of hormones?
- Water Soluble
2. Lipid Soluble
What is the WATER soluble class of hormones?
- typically modified peptides or amino acids
- MOST hormones are water-soluble
- water-soluble molecules CAN’T pass through lipid bilayer membrane - b/c they are POLAR
- (ex: cell or nuclear membranes)
- (CAN be stored in vesicles - b/c they can’t pass through a membrane)
- NEED a RECEPTOR molecule
- CAN float freely through the interstitual tissue & through blood (b/c mostly water)
What are examples of WATER soluble hormones?
- growth hormone
- insulin
- leptin
- oxytocin
What is the LIPID soluble class of hormones?
- steriod hormones
- many peptide hormones, most amine (made of amino acids) hormones, all lipid hormones
- lipid-soluble molecules CAN pass through lipid-bilayer cell membrane (& nuclear membrane) (CANNOT be stored in vesicles)
What are examples of LIPID soluble hormones?
- androgens
- estrogens
- progestogens
= sex hormones
In order for hormone delivery…
a gland “broadcasts” a chemical message (ex: secretes hormone)
What is the hormone delivery process for WATER soluble hormones?
- actively removed from secretory cells
- must bind to surface receptor molecule on target cells
What is the hormone delivery process for LIPID soluble hormones?
- hormone just floats out of secretory cell
- MUST be bound to carrier protein to become water-soluble
- just floats into target cell
Lipid-soluble hormones don’t have to be actively exported into the interstitial fluid because…
they just flow through following concentration gradients out of the cell & into the interstitial fluids, can leak into blood but need transport proteins (carrier proteins)
- b/c they are not water soluble (can’t dissolve any blood so attach to carrier molecules that makes it water soluble, then it can dissolve in blood & flow in blood like water-soluble)
What makes the WATER soluble hormone go from interstitial fluid into the bloodstream for instance?
it’s following the CONCENTRATION GRADIENT!!!
- when it is dumped into the interstitial fluid there is a bunch of hormone there & not in the blood so it will leak into the blood vessel
- it will flow the concentration gradient down into the blood vessel
- & other places in the body they follow the concentration gradient out of the blood & into the interstitial fluid & find receptor molecule
What is the signal transduction process for WATER soluble hormones?
- receptor molecules are typically GPCRs (G protein-coupled receptor)
- do secondary messenger system, bind to the receptor molecule which sends a G protein along the cell membrane to activate other membrane receptor molecules that sends secondary messenger molecules into the cell to do various things like gene expression, modify proteins etc.
ex: stress response
- do secondary messenger system, bind to the receptor molecule which sends a G protein along the cell membrane to activate other membrane receptor molecules that sends secondary messenger molecules into the cell to do various things like gene expression, modify proteins etc.
What is the signal transduction process for LIPID soluble hormones?
- NO receptor molecule on target cell membrane (b/c flows right through)
- hormone typically binds to free-floating receptor in cytoplasm
- hormone-receptro complex floats into nucleus
- acts as transcription factor
ex: vitellogenin upregulation
Why are brains described as a “black box”?
produces specific output for specific input
ex: when a mosquito lands on you, you sqat it, and don’t have to know what is going on in your brain in order to know what will happen
The PNS & the CNS are both ectoderm but…
arise from different parts
- CNS comes from neural tube
- PNS comes from neural crest cells (develop independently)
Sensory input
stimulus observed
Motor output
any nervous system output (muscle movement, gland secretion, etc)
Effector cell
any neuron that produces motor output (including muscle cells)
Central Nervous System
the brain & spinal cord; information processing occurs here
Peripheral Nervous System
all other neurons; the PNS connects the CNS to the sensory & effector cells (& thus to the outside world)
- connects brain to outside world
A reflex arc
ex of a black box (an input-output circuit)
- something happens & you reflexively produce an output (no thought, no mediation, no learning, can’t control it, automatic)
WHOLE PROCESS IN SPINAL CORD (not in brain)
What is the process for the reflex arc?
- your tendon is pulled, stretching the quadriceps above
- stretch receptors in your quadriceps are activated & send a signal to a ganglion in the spinal cord
- “thinking” your lower leg just moved inward, the cell activates 2 other cells
- the 1st is a motor neuron that causes the quadriceps to contract
- the 2nd is an inhibitory interneuron
- the motor neuron controlling the hamstring is thus inhibited
- with the quadriceps activated & the hamstring inhibited, the lower leg suddenly extends
- b/c the tendon is stretched only briefly, the action ends as quickly as it began
What are ex’s of reflex arcs that DO NOT involve the brain at all (all in spinal cord=faster)?
- patellar reflex (“knee jerk”)
- someone tickles the bottom of your foot?
your ankle flexes - touch the palm of a baby’s hand?
she closes her hand - touch something hot?
your arm immediately pulls back
What are ex’s of reflex arcs that DO involve your brain (not consciously though)?
- turn your head right?
your eyes move left - start falling forward?
your arms raise up
Axon terminal
output end
- end of axon, where they signal to something else (to another neuron or muscle cell or gland cell etc)
Synapse
connection b/t 1 cell & another
Synaptic cleft
is space b/t synapse
If the axon is in PNS it’s a myelin sheath provided by…
schwann cell
If the axon is in CNS it’s a myelin sheath provided by…
oligodendrocyte
Axosomatic synapse
the synapse connects the axon of 1 cell to the soma (cell body (of another)
Axodendritic synapse
goes from an axon to a dendrite
- mostly this one
Axoaxonic synapse
goes from an axon of 1 cell to another
- 1 cell basically the output of the other cell
How many cells in the brain are neurons?
only about half (& there are about 86 billion neurons!)
- the rest are glia (“glue”)
- except they are not just glue!
What are the 3 main types of glia?
- schwann cells
- oligodendrocyte
- astrocyte
What is the main purpose of the insulation (myelin sheath)?
to help the transmission of the action potential down the axon
- make the axon much faster than it would be
- so it’s insulating
- they’re filled with lipids (mostly fat) so provide a lot of insulation
Why are all machinery of action potential at the nodes of ranvier?
b/c wrapped of myelin sheath, which make the axon much faster than it would be
Describe an oligodendrocyte (glial cell)
myelin sheath in the CNS
- some primary differences are:
the oligodendrocyte reach out & wrap around axon in multiple places (sometimes even multiple neurons) & provide insulation
Describe an astrocyte (glial cell)
myelin sheath in the PNS
- caretakes of neuron
- feed neuron
- provide blood-rained barrier (don’t let anything in if it’s not safe)
- keep pathogens out
- they decide what is safe to give to the brain cells, the neurons, & what is not safe
What does the nernst equation provide us with?
the equilibrium potential for a particular ion is calculated by this
- it is the voltage across the membrane that would result in 0 net movement of that ion
What is z in the nernst equation?
charge of the ion!
- should be (-)
Neurons & muscle cells are…
“excitable” - AKA their voltages can change
What does it mean for neurons & muscle cells to be “excitable”?
- they maintain a (-) voltage compared to the interstitial space outside the cell
- typically they briefly change voltage (get “excited”) in order to do work
- maintaining a (-) voltage takes a TON of energy (ATP)
How much of the brain does the brain consume of the body’s energy at rest?
20%
The pump pumps…
2 K+ ions for every 3 Na+ ions (uses 1 ATP molecule)
- this maintains concentration gradient
What does change in voltage allow for?
info processing & info transmission
How many neurons does the C.elegans have?
only 304 neurons, but they produce only graded potential
- NO action potentail
What is graded potential?
voltage just changes, just gradually goes up & down (voltage rises in a continuous manner)
What only produce only graded potential?
- vertebrate retinal cells
- c. elegans
- but all neurons are graded until they “fire”
Resting Membrane Potential
the membrane potential characteristic of a nonconducting excitable cell, with the inside of the cell more negative than the outside
Example for Negative feedback
- in the case of secretin signalling, the release of bicarbonate by the pancreas increases pH in the intestine, eliminating the stimulus & thereby shutting off the pathway
- by decreasing or abolishing hormone signalling, NFB regulation PREVENTS excessive pathway activity
Examples for Positive feedback
- the oxytocin pathway
- in response to the circulating oxytocin, the mammary glands secrete milk
- milk released in response to the oxytocin leads to more suckling & therefore MORE simulation
- activation of the pathway is sustained until the baby stops sucking
- when mammals gives birth, muscle contraction triggers release of oxytocin, which induces uterine muscles to contract more strongly
Hormone pathways involved in homeostasis typically involve which feedback loop?
negative (helps restore a preexisting state)
What is part of the Central Nervous System AND where is it formed from?
- the brain & spinal cord
- from neural TUBE
What is the Peripheral Nervous System AND where is it formed from?
- everything else
- from neural CREST CELLS
Grey Matter vs White Matter?
grey matter:
- large #’s of neuronal cell bodies
white matter:
- large bundles of axons (“nerve”)
Why does white matter LOOK white?
b/c the axons myelinated, & myeline has lots of lipids (which provides good insulation)
Neural vs Non-Neural parts of the Nervous System?
neural (the neurons)
- the nervous system includes approx 8.6x10^10 in HUMANS
- these neurons form approx. 1.5x10^14 synapses with 1 another
- extreme amount of possible connections
non-neural
- probably similar # of glial cells as neurons, of 5 types
- astrocytes
- microglia
- ependymal cells
- oligodendrocytes
- schwann cells
- ventricles
- central canal
- cerebrospinal fluid
- meringes
What are astrocytes?
a non-neural part of NS
- feed, modulate, & protect neurons in with associate with BBB (blood brain barrier)
What are microglia?
a non-neural part of NS
“immune” system
- act as immune cells (fight infections)
What are ependymal cells?
a non-neural part of NS
- makes CSF (cerebrum spinal fluid), lines vesicles
What is oligodendrocytes?
a non-neural part of NS
- myelin sheath
what is schwann cells?
a non-neural part of NS
- myelin sheath
Which non-neural parts of the NS are part of the CNS?
- astrocytes
- microglia
- ependymal cells
- oligodendrocytes
Which non-neural parts of the NS are part of the PNS?
schwann cells
Ventricles
a non-neural part of NS
- 4 fluid-filled (CSF) spaces in the MIDDLE of the brain
Central canal
a non-neural part of NS
- fluid-filled canal DOWN centre of the spinal cord
Cerebrospinal fluid
a non-neural part of NS
- fluid that flows THROUGH ventricles & central canal & B/T the meninges
- derived in brain from arterial blood by ependymal glial cells
- drains back into veins
- sort of an “extra” circulatory system for the brain
- also provides cushioning for the brain
What is sort of an “extra” circulatory system for the brain?
cerebrospinal fluid
Meringes
extra layers of connective tissue to protect the CNS
CNS
“black box”; high level processing that takes input from outside world via the PNS & produces an output
PNS
connects everything to the CNS
What are the input/output, systems, & divisions of the PNS?
- sensory input
- motor output
- motor systems
- autonomous systems
- sympathetic division
- parasympathetic division
- enteric division
Sensory input vs motor output?
sensory input: ALL sensory organs
motor output: muscle & glandular output from NS
Motor systems vs autonomous systems?
motor systems: voluntary skeletal (conscious)
autonomous systems: involuntary (can’t control - unconscious)
Sympathetic Division vs Parasympathetic Division vs Enteric Division?
sympathetic division: fight or flight
parasympathetic division: rest & digest
enteric division: digestion
What is part of the FOREbrain?
- cerebrum
- diencephalon (thalamus, hypothalamus, posterior pituitary, pineal gland)
What is part of the MIDbrain?
midbrain lol
What is part of the HINDbrain?
- pons, cerebellum
- medulla oblongata
Cerebral cortex
outer region/layer of cerebrum
What are components of the brainstem?
- MIDbrain
- Pons
- Medulla
The cerebrum
(big part)
- right half controls left body, & vice versa
- corpus callosum connects hemispheres
- FRONT half = decision making & MOTOR control
- BACK half = processes SENSORY info
- basal nuclei holds “muscle memory” - executes motor programs
Corpus callosum
connects hemispheres
- part of cerebrum
Front half of cerebrum vs back half?
- front half = decision making & MOTOR control
- back half = processes sensory info
What is the basal nuclei/ganglia role?
holds “muscle memory” - executes motor programs
- part of cerebrum
What happens if the BASAL NUCLEI is damaged from tumour or brain injury?
then those pre stored motor programs aren’t available anymore
- can still (for ex) pick up a cup of coffee but would have to CONCENTRATE like you have NEVER done it before
Cerebellum & basal nuclei together…
coordinate movement!
The cerebellum
(little brain at back)
- mostly responsible for ERROR-CORRECTION of MOTOR OUTPUT
- also involved in emotion in humans (not fully understood)
- compare sensory with motor to make sure you don’t spill something etc.
What happens if the CEREBELLUM is damaged from tumour or brain injury?
you CAN still pick up coffee mug for ex
- you don’t have to think about it but you do have to b/c you don’t have automatic error correction anymore, you would have VERY LITTLE CONTROL
The diencephalon
- the thalamus is the “switching station” for incoming sensory signals
- almost all SENSORY info arrives in the thalamus & is SORTED to different brain regions
- the hypothalamus is the major neuroendocrine organ
- the pituitary gland & pineal gland are also important neuroendocrine organs
Thalamus
is the “switching station” for incoming SENSORY signals
- part of the diencephalon
Hypothalamus
is the major neuroendocrine region (issues secretion of hormones)
- part of the diencephalon
Pituitary gland & pineal gland
important neuroendocrine organs
- part of the diencephalon
What are 3 important neuroendocrine organs/region?
- Hypothalamus
- Pituitary gland
- Pineal gland
The brainstem
- CONNECTS the brain TO the spinal cord
- does a lot of SORTING of SENSORY INFO
- the pons & the medulla
Pons & the medulla
both involved in LOW LEVEL INFO PROCESSING (“primitive” functions = UNCONSCIOUS functions)
- homeostasis
- moving info around diff parts of the brain
- automatic behaviour like breathing, swallowing, etc
Where is the HIGHEST level of info processing?
in the brain
MAMMALS have unusually LARGE cortices compared to other…
vertebrate
PRIMATES have unusually LARGE cortices compared to other…
mammals
HUMANS have unusually LARGE cortices compared to other…
primates
Left brain vs right brained?
- it is TRUE that some brain function occur on 1 side or the other…but NO, that’s an exaggeration
- YES language processing is usually on the left & music processing is usually on the right etc.
- but no 1 is dominant on 1 side or the other
- & sidedness differs in the population
Neuroendocrine system
- the hypothalamus is a major endocrine organ
- (hypothalamus & neuroendocrine system) interface b/t neurons & endocrine systems
- also interface b/t nervous & circulatory systems
- many of its hormones target the PITUITARY GLAND
- many PITUITARY HORMONES target other ENDOCRINE ORGANS (they’re trophic)
- pineal gland
Why is the neuroendocrine system interface b/t nervous & circulatory systems?
b/c this is 1 of the very few parts of the brain where brain cells have direct access to the blood to test the status of the blood without the blood brain barrier (BBB) being in the way
Pineal gland
largely responsible for sleep patterns (part of neuroendocrine system)
Hypothalamus
- “command centre” of the endocrine system
- some endocrine circuits do NOT involve hypothalamus
Just like the brain is the “command centre” of the NS, the HYPOTHALAMUS is the “command centre” of the …
endocrine system
Just like some neural circuits do NOT involve the brain, some endocrine circuits do NOT involve the…
hypothalamus
Hypothalamus connects to the…
pituitary gland
What are the 2 lobes of the pituitary gland?
- posterior pituitary
2. anterior pituitary
The POSTERIOR pituitary gland
- AN extension of the hypothalamus (same tissue)
1. neurosecretory cells span FROM HYPOTHALAMUS into posterior pituitary
2. hormone SECRETED INTO INTERSTITIAL FLUID in posterior pituitary
3. hormones taken up BY blood in capillary bed (& transported to rest of body)
What are the 2 hormones secreted in the POSTERIOR pituitary gland AND what do they target?
- Antidiuretic Hormone (ADH):
Target: kidney tubules (& stimulates retention of water) - Oxytocin:
Target: mammary glands, uterine muscles
The ANTERIOR pituitary gland
- NOT an extension of the hypothalamus (NOT same tissue)
1. NEUROSECRETORY CELLS secrete specific tropic hormones into the INTERSTITIAL FLUIDS of the HYPOTHALAMUS itself
2. Hormones picked up by blood in the capillary bed WITHIN the hypothalamus
3. Blood transports hormones VIA PORTAL VESSELS to the anterior pituitary gland
4. The hypothalamic tropic hormones then stimulate secretory cells to RELEASE other hormones into the interstitial fluid (OF THE pituitary gland)
What are the 6 hormones secreted in the ANTERIOR pituitary gland AND what do they target?
- Follicle-Stimulating Hormone (FSH) & Lutenizing Hormone (LH)
Target: gonads - Thyroid-Stimulating Hormone (TSH)
Target: thyroid gland - Adrenocorticotropic Hormone (ACTH)
Target: adrenal cortex - Prolactin
Target: mammary glands - Melanocyte-Stimulating Hormone (MSH)
Target: melanocytes (melanin-producing cells in skin) - Growth Hormone (GH)
Target: pretty much everything
The hypothalamic-pituitary-thyroid (HPT) axis (hormone signally cascade)
the brain detects DROP in thyroid hormones levels (T3 & T4):
in response:
- hypothalamus –> TRH
- anterior pituitary –> TSH
- thyroid (thalamus) –> T3 & &4
- rest of body
- these close a NEGATIVE feedback loop
The hypothalamic-pituitary-adrenal (HPA) axis (hormone signally cascade)
under certain types of stress (ex: low blood sugar):
in response:
- hypothalamus –> CRH
- anterior pituitary –> ACTH
- adrenal cortex –> corticosteroids
- rest of body
- NEGATIVE feedback loop
What are the 2 types of corticosteriods?
- GLUCOcorticoids:
- causes proteins & fats to be broken down & converted to GLUCOSE
- causes immune system to be suppressed - MINERALcorticoids
- causes kidneys to retain SALTS & water
- causes increased blood pressure & volume
What are the 4 hypothalamus-pituitary axes?
- Hypothalamic-pituitary-THYROID (HPT) axis
- Hypothalamic-pituitary-ADRENAL (HPA) axis
- Hypothalamic-pituitary-GONADAL (HPG) axis
- last step involves producing estrogen & testosterone (in the gonads) - Hypothalamic-pituitary-SOMATOATROPIC (HPS) axis
- the last step involves secreting growth hormones (GH)
Growth hormones (GH) is both…
trophic & nontrophic
- it stimulates production of hormones in other glands but also just have direct effects on pretty much all tissues causing them to grow
What happens if you have too much or too little Growth hormones (GH)?
- if you have too much GH you end up being too big
- often associated with reduced lifespan
- if there is too much GH the organs just can’t keep up (too much body)
- if too little, the organs are too big (the tissues don’t grow at the same rate)
- can be treated with more GH easier
Fight or Flight response
- epinephrine & norepinephrine AKA adrenaline & noradrenaline
- causes glycogen to be broken down to glucose
- cause increased:
- blood pressure
- heart rate
- breathing rate
- metabolic rate
- blood flow to brain & muscles
- DECREASED blood flow to gut organs (don’t need to digest food rn)
brain detects problem –> sends neural signal to adrenal medulla –> sends epinephrine & norepinephrine –> to rest of the body
Oxytocin’s cross-species effects
“love hormone”
- acts as a hormone
- acts as a neurotransmitter
- mediates lactation
- mediates ejaculation
- mediates labour contractions
- promotes social bonding (b/t mother & baby)
- promotes contraspecific bonding! (when puppy & you staring in each other eyes)
Graded Potential (no change)
if no activity of cell, then voltage remains the same
- the membrane potential will just stay at RMP
Graded Potential (small depolarization) Na+ influx
- if a Nat+ ion channel for ex, were to open, little bit of Na+ would flow in & voltage would go UP
- if Na+ channel closes pretty quickly, the Na+-K+ pump & the leaky ion channels will restore the membrane potential
Graded Potential (small hyperpolarization) (Cl- influx)
if it is a Cl- ion that flow into the cell, (-)ly charged so voltage will go DOWN
- means there will be a small hyperpolarization, & as long as that ion channel closes pretty quickly it’s going to be a very brief event
Graded Potential (no change “cancelled charges”)
K+ efflux
Na+ influx
if you have a Na+ & K+ ion enter the cell at the SAME TIME
- K+ & Na+ ion channels open & it is the same flow rate so nothing is going to change
- b/c you will have the SAME # of Na+ GO IN as K+ GO OUT (AKA (+) charge going in & (-) out), so NO NET VOLTAGE change
- as a result, membrane potential isn’t gonna vary from RMP
Graded Potential (larger depolarization - Spatial Summation) Na+ influx
- if you have SEVERAL ion channels open ALL at ONCE AROUND the cell
- all ion channels open briefly & (+) charges will flow into the cell at the SAME TIME, & so you can just sum them up
- since there is a LOT in there at a brief time the depolarization will be much larger b/c ion channels are letting a lot of Na+ in real fast
Graded Potential (larger depolarization - Temporal Summation) Na+ influx
- if a single ion channel or smaller # of ion channels in the SAME PLACE REPEATEDLY open
- each little depolarization is gonna hit BEFORE the next one gets restored & voltage keeps going UP
- b/c leaky channels & Na+-K+ pump won’t be able to put everything back to normal before ion channel opens again
Graded Potential (much larger depolarization) Na+ influx
if you have HUGE amounts of activity BOTH SPATIALLY & TEMPORILY ALL OVER the cell, MASSIVE amounts of Na+ is gonna flow in & voltage will rise very rapidly & very high
- SUM changes BOTH spatially & temporally & voltage is gonna go UP really quickly
Action Potentials
- once enough activity RAISES membrane potential ABOVE threshold (usually by Na+ influx)…an action potential results
- usually results in massive INCREASES in Na+ influx
Resting Membrane Potential (for Action Potential)
INITIAL
- at rest, the leak channels & Na+/Na+ pump maintain RMP (typically -70mV)
- voltage-gated ion channels are CLOSED
Depolarization (for Action Potential)
- some events causes NON-voltage-gated Na+ channels to OPEN (ex: neurotransmitters from upstream neuron or some kind of sensory signal in sensory neurons)
- membrane potential begins to RISE/depolarize (graded potential)
- 1 membrane potential PASSES THRESHOLD (typically -55mV), voltage gated Na+ channels RAPIDLY OPEN
- Na+ RUSHES IN
- further INCREASED voltage causes additional voltage-gated Na+ channels to OPEN
- the membrane potential shoots up to (approx +30mv)
NEGATIVE FEEDBACK LOOP
Repolarization (for Action Potential)
- most voltage-gated Na+ automatically become INACTIVATED VERY QUICKLY
- most voltage-gated K+ channels are FINALLY OPEN (they’re much slower)
- Na+ STOPS flooding in; K+ BEGINS flooding OUT, rapidly repolarizing the cell
- no inflow of + ions, HUGH outflow of - ions (curve goes down)
Hyperpolarization (for Action Potential)
- b/c K+ are so slow, the cell undershoots the RMP before they finally CLOSE
- further INCREASED voltage causes additional voltage gated Na+ channels to OPEN
- the low voltage causes the Na+ channel to CLOSE PROPERLY (it’s BELOW threshold)
Resting Membrane Potential (for Action Potential)
FINAL
- eventually the much slower voltage-gated K+ channels CLOSE
- the leaky channels & Na+/K+ pump bring everything back to RMP (-70mV)
- if the original signal is still present (or returns), this will all immediately repeat itself
Action Potential Propagation
axon hillock —> axon terminal
- if it depolarizes to the point of reaching threshold voltage of the particular neuron type, then an action potential forms AT AXON HILLOCK (where axon starts at soma)
1. when cell is doing nothing axon also does nothing at RMP
2. if an event occurs that increases membrane potential inside the Na+ ion channels open, flooding into axon increasing voltage & in near by regions
3. then those voltage gated channels open next & Na+ flows in there then close quick - K+ channels open slowly letting it out
- with Na+ channel closed & K+ channel open, the voltage drops way down (-)
4. with an action potential here, it will trigger an axon potential beside, DISABLING Na+ channel behind it (letting K+ out - voltage drops)
5. repeats over again
What are the 2 types of Synapses, briefly COMPARE?
- Electrical Synapses (i.e. gap junctions)
- in vertebrates & invertebrates
- sparse (b/c HARD TO CONTROL)
- NOT easy to modulate - Chemical Synapses
- in vertebrates & invertebrates
- the PREDOMINANT type of synapse
- very plastic, EASY to modulate
How can they control how likely an action potential jumps from 1 cell to another?
by changing the # of receptor molecules or vesicles etc.
DESCRIBE Electrical Synapses (gap junctions)
- connect the cytoplasm of adjacent neurons
- membranes of adjacent neurons are CONTINUOUS!
- action potentials pass from 1 neuron to the next (as if one), travelling along that membrane
- analogous to plamodesmata in plants
DESCRIBE Chemical Synapses
- action potential arrives at axon terminal
- voltage-gated Ca2+ channels OPEN
- influx of Ca2+ causes synaptic vesicles to fuse with cell membrane
- neurotransmitter is released (exit) into synaptic cleft & binds to neurotransmitter-gated Na+ channels on POSTsynaptic cell
- influx of Na+ causes excitatory POSTsynaptic potential (EPSP)
Removal of Neurotransmitter (diff ways)
- natural breakdown
- enzymatic breakdown
- diffuse away
- uptake into glial cell
- re-uptake into PREsynaptic cell
Neurotransmitters (3 main points)
- there are TONS of diff neurotransmitters of many diff types
- neurotransmitters are NOT excitatory/inhibitory, the receptor molecules ARE
- diff animals evolved to use neurotransmitters in diff ways for EXACT same chemicals
EX: insects & mammals have almost exact same suite of neurotransmitters but we use them in diff ways
Different types of Neurotransmitters
- Amino Acids
- glutamate, aspartate, glycine, GABA, etc - Gases (simplest - flow freely)
- NO, CO, H2S, etc - Monoamines
- dopamine, epinephrine, histamine, serotonin, etc - Peptides (proteins)
- oxytocin, substance P, endogenous opioids, etc - & others
- acetylcholine, etc
In invertebreates;
ACh is primarily the neurotransmitter in…
Glu is typically the neurotransmitter in…
- motor neurons
- the brain
in insects!
- other way around!
When does an action potential occur?
whenever a depolarization INCREASES the membrane voltage to a particular value (threshold)
Where do sensory neurons come from?
Sensory neurons are part of the PNS, which derives from the neural crest cells (ectodermal tissue).
Cells can communicate to other cells that are far away in the body with the use of which systems?
Cells can communicate (depending on their cell type) with other far away cells either via a neural signal (a direct line from the sending cell to the receiving cell or cells) or via the endocrine system (releasing hormone into the bloodstream which will go everywhere in the body).
How is neurotransmitter signalling terminated?
both receptor activation & postsynaptic response cease when neurotransmitter molecules are cleared from the synaptic cleft
- the removal of neurotransmitters can occur by simple diffusion or by other mechanisms
What is presynaptic cell and postsynaptic cell?
The cell that delivers the signal to the synapse is the presynaptic cell. The cell that will receive the signal once it crosses the synapse is the postsynaptic cell. Since most neural pathways contain several neurons, a postsynaptic neuron at one synapse may become the presynaptic neuron for another cell downstream.
Where does an action potential start?
axon hellock
- then shoots down along membrane of axon
- toward axon terminal & dendrites of next neuron
