neural communication Flashcards
(actually in animal responses) until i say so
what is the central nervous system?
-brain
-spinal cord
what is the peripheral nervous system?
-sensory neurones carrying sensory information from the receptors to the CNS
-motor neurones
what does the peripheral nervous system branch into?
-somatic nervous system
-autonomic nervous system
what is the somatic nervous system?
-voluntary, conscious activities eg. running
-most neurones are myelinated
-stimulates skeletal muscle
what is the autonomic nervous system?
-involuntary, unconscious activities eg. digestion
-most neurones are non-myelinated
-stimulates smooth muscle in the gut wall, cardiac muscle and glands
what is the autonomic nervous system branched into?
-sympathetic nervous system
-parasympathetic nervous system
what is the sympathetic nervous system?
-prepares body for ‘fight or flight’ response eg increases heart rate
-neurones secrete the neurotransmitter noradrenaline at the synapse between the neuron and the effector
what is the parasympathetic nervous system?
-calms the body down and prepares it for ‘rest and digest’ eg. decreased heart rate
-parasympathetic neurones secrete the neurotransmitter acetylcholine between the neurone and effector
what is the hypothalamus?
-automatically maintains body temperature and homeostasis at the normal level
-produces hormones that control the pituitary gland
what is the pituitary gland?
-controlled by the hypothalamus
-releases hormones and stimulates other glands to release their hormones
what is the medulla oblongata?
-at the top of the spinal cord
-automatically controls breathing rate and heart rate
what is the cerebrum?
-the largest part of the brain
-it’s divided into two cerebral hemispheres
-the cerebrum has a thin outer layer called the cerebral cortex which is highly folded
-the cerebrum is involved in vision, hearing, learning and thinking
what is the cerebellum?
-the cerebellum has a folded cortex
-important for muscle coordination, posture and coordination of balance
(now in neural communication)
what do sensory neurons carry?
structure?
myelinated or non-myelinated?
-carry impulses from the sensory receptor to relay and motor neurons
-long dendron that carries the impulse from the sensory receptor cell to the cell body and then an axon carries it from the cell body to the next neurone
-myelinated
what is a myelin sheath?
what kind of biological molecule is it?so?
what is saltatory conduction?
what does this mean?
-Schwann cells wrap around the axon to form a myelin sheath
-a lipid so doesn’t allow charged ions to pass through it
-when the impulse just from node to node (from each node of Ranvier which are the gaps between the myelin sheath).
-that the action potential travels along the axon faster as it doesn’t have to generate an action potential along the entire axon, just the nodes of Ranvier = increasing the speed of impulse transmission
what do relay neurons carry?
structure?
-carry impulses between the sensory and motor neurons
-multiple short axons and dendrons
what do motor neurons carry?
structure?
and transmit the impulse where?
-carry the impulse from relay or sensory neurons to effectors (muscle or glands)
-have a long axon and multiple short dendrons and an axon terminal
-away from the cell body
what are sensory receptors?
what do they carry?
what are the 3 types of sensory receptors? and what do they detect?
-they detect a stimulus, these cells are transducers, converting different types of stimuli into electrical nerve impulses
-impulses from a receptor to the CNS
-photoreceptors (rods and cone cells) = light
-thermoreceptors (skin) = heat
-mechanoreceptor (pacinian Corpuscle in skin) =pressure
what is the Pacinian Corpuscle?
where are they?
what does it consist of?
what do the channel proteins allow?
what will the channels do?
-receptors that respond to pressure changes
-deep in the skin, mainly fingers and feet
-a single sensory neurone wrapped with layers of tissue separated by gel and the sensory neurone in the pacinian corpuscle has special channel proteins in its plasma membrane
-allow ion transportation and the membrane’s surrounding the sensory neurones have stretch-mediated sodium channels
-they will open and allow sodium ions to diffuse into the sensory neurone ONLY when they are stretched and deformed.
sensory neurone resting state?
when pressure is applied?
-the sodium-ion channels are too narrow for the sodium ions to diffuse into the sensory neurone so the resting potential is maintained
-when pressure is applied = the stretch-mediated sodium ion channels are deformed and widen = allowing sodium ions to diffuse in which leads to the establishment of a generator potential
explain resting potential-
-when a neurone is not conducting an impulse there is a difference between the electrical charge inside and outside of the neurone = this is resting potential
-there are more sodium and potassium ions outside of the neurone compared to the inside so the inside is more negative at -70mV
-the resting potential is maintained by a sodium-potassium pump which uses active transport and therefore ATP
-the pump moves 2 potassium ions in and 3 sodium ions out, creating an electrochemical gradient causing potassium to diffuse out and sodium to diffuse in
-however the membrane is more permeable to potassium so more potassium diffuses out resulting in the -70mV
what is an action potential?
what is the refractory period?
An action potential is when the neuron’s voltage increases beyond a threshold from resting potential. This generates a nervous impulse. The increase in voltage (depolarisation) is due to the neurone membrane becoming more permeable to sodium ions
-during repolarisation and hyperpolarisation the neuron cell membrane cannot respond to another stimulus
describe an action potential (mark scheme)-
-generator potential causes first sodium ion channels to open
-if enough sodium ions move into the axon to reduce the potential difference to the threshold value
-which is -55mV
-then, voltage dependent sodium channels open and sodium ions move into the axon
-more sodium ions move in, so more sodium ion channels open, this is an example of positive feedback
-this is called the ‘all or nothing’ principle as all the sodium ion channels open if the threshold is reached
-the potential difference is now +40mV as it becomes more positive inside the axon compared to the outside
-this is depolarisation
-the sodium voltage dependent channels close which is the absolute refractory period
-voltage dependent potassium channels open and potassium ions move out of the axon
-the membrane repolarises
-the potassium ion ‘overshoot’ causes hyperpolarisation
-the voltage is now more negative than resting potential
-enabling the impulse to only flow in one direction
-the resting potential is re-established because potassium ions diffuse back into the cell as sodium-potassium pump switches back on
-this wave of depolarisation-repolarisation- hyperpolerisation repeats itself down the axon
-the myelin sheath speeds up conduction as it is an electrical insulator
-because the current can jump between the nodes of Ranvier, this is the saltatory effect
what is a wave of depolarisation?
what does this cause?
-when an action potential happens, some of the sodium ions that enter the neurone diffuse sideways = causing the sodium ion channels in the next region of the neurone to open and sodium ions diffuse into that part
-a wave of depolarisation to travel along the neurone
-and then the wave moves away from the parts of the membrane in the refractory period because these parts can’t fire an action potential
