Chapter 13 - Neuronal Communication

To transmit electrical impulses rapidly around the body to allow the organism to respond to changes in internal and external environment

Cell body, Dendron, axon,

contains the nucleus surrounded by cytoplasm. large amounts of endoplasmic reticulum and mitochondria which are involved in the production of neurotransmitters

chemicals used to pass signals from one neurone to the next

-short extensions which come from the cell body. divide into smaller branches AKA denrites. -To transmit electrical impulses towards the cell body.

-Singular elongated nerve fibres. can be v long e.g. those that transmit impulses from the tips of toes and finger to the spinal cord

-cylindrical in shape, consisting of a very narrow region of cytoplasm surrounded by plasma membrane -To transmit electrical impulses away from the cell body

To transmit impulses from a sensory receptor cell to a relay neurone, motor neurone or the brain.

Has one dendron, which carries the impulse to the cell body, one axon which carries the impulse away from the cell body

To transmit impulses between neurones. e.g. sensory neurones and motor neurones. short axons and dendrons

To transmit impulses from a relay or sensory neurone to an effector, e.g. muscle/gland. one long axon and many short dendrites

receptor --> sensory neurone --> relay neurone --> motor neurone --> effector cell

Neurones that have axons covered in myelin sheaths the myelin sheath acts as an insulating layer and allows these myelinated neurones to conduct the electrical impulse at a much faster speed than unmyelinated neurones

Schwann cells grow around the axon multiple times, surrounding the axon with layers of membrane

Node of Ranvier

Cause signal to jump which allows faster rate of transmission

No nodes of Ranvier so no jumping, continuous transmission is much slower

Mechano, chemo, thermo, photo

Pressure, movment e.g. pacinian corpuscle receptor (detects pressure)

Olfactory receptor

End bulbs of Krause

Tongue

Specific to a single type of stimulus, transducers

Sensory receptors convert stimulus into a nerve impulse (Generator potential)

End of neurone surrounded by layers of connective tissue separated by layers of gel, sodium ion channels in membranes, stretch-mediated sodium channels

Sodium ion channels too narrow in a normal state, resting potential present, corpuscle changes shape when pressure applied to the corpuscle, membranes stretch, channels widen, sodium ions diffuse in, membrane depolarises, generates generator potential, generator potential creates action potential

The potential difference across a neurone's membrane when it isn't transmitting an impulse

Outside the membrane

3 sodium ions actively transported out of the axon and 2 potassium ions actively transported in by sodium potassium pump, more sodium ions outside the membrane and more potassium ions inside the cytoplasm, sodium ions try to diffuse in and potassium ions try to diffuse out, gated sodium ion channels closed so sodium ions can't diffuse, potassium ions can move freely, more positive ions outside than inside

-70mV

Change in potential difference across a membrane from negative to positive

Receptor cells respond to stimuli, gated sodium ion channels open, larger stimuli will open more channels, sodium ions diffuse into the axon, inside of neurone is less negative, change in potential difference across the membrane is a generator potential

Generator potential reaches threshold

Voltage gated Na+ channels open

Lots of Na+ diffuse into the axon (Positive feedback)

Membrane depolarised, voltage gated Na+ channels close

Voltage gated K+ channels open

K+ diffuse out of membrane and become depolarised

Potential difference overshoots

Membrane becomes hyper polarised

Resting potential restored by sodium potassium pump

Refractory period

The diffusion of sodium ions into the axon when doing a generator potential will open voltage-gated sodium ion channels so more sodium ions diffuse in

-50mV

+40mV

Refractory period

To allow cell to recover, to only allow action potentials to be transmitted in one direction

Depolarisation happens at the nodes of Ranvier, sodium ions pass through protein channels at the nodes, localised circuits between nodes, action potential jumps from one node to another

Saltatory conduction

Faster as fewer places where channels have to open, more energy efficient as less repolarisation so less ATP required

If a stimulus crosses a threshold value, a response will always be triggered. If it doesn't, no action potential will be triggered. Size of action potential not affected by the size of the stimulus

Larger stimuli cause more action potentials to be generated in a given time, increasing frequency, increasing degree of response.

Synaptic cleft, presynaptic neurone, postsynaptic neurone, synaptic knob, synaptic vesicles, neurotransmitter receptors

20-30 nm

Mitochondria, large amounts of endoplasmic reticulum

Excitatory, inhibitory

Neurotransmitters that result in the depolarisation of the postsynaptic membrane

Neurotransmitters that result in the hyperpolarisation of the postsynaptic membrane

Acetylcholine

GABA

Action potential reaches end of presynaptic neurone, depolarisation causes calcium ion channels to open, calcium ions diffuse to knob, vesicles containing neurotransmitters fuse with membrane, released by exocytosis, diffuse over, bind with receptor on the membrane, sodium ion channels open, sodium ions diffuse into neurone, triggers action potential, propagated along the neurone

Prevents response from happening again, neurotransmitter can be recycled

Acetylcholine is the neurotransmitter, hydrolysed by acetylcholinesterase, breaks down to choline and ethanoic acid, reformation requires ATP

Ensuring impulses are unidirectional, allow impulse from one neurone to be transmitted to a number of neurones, allow an impulse from a number of neurones to feed into one

When the amount of neurotransmitter builds up to reach the threshold to trigger an action potential

Spatial, temporal

When a number of presynaptic neurones are connected to one postsynaptic neurone

When a single presynaptic neurone releases neurotransmitter several times over a short period as a result of several action potentials

Brain and spinal cord

The neurones that connect the CNS to the body,

Somatic and autonomic nervous systems

System under conscious control, carries impulses to the muscles

System under subconscious control, carries impulses to glands and smooth muscle and cardiac muscle

Sympathetic and parasympathetic nervous systems

Protected by the skull, surrounded by meninges, five main areas

Cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland

To receive sensory information and interpret it with respect to previous experiences, to send impulses along motor neurones to act on the information, used to control both voluntary and involuntary responses

Highly convoluted, split into two halves, has discrete areas for different functions, outer layer called cerebral cortex

Impulses from right side of the field of vision sent to left hemisphere, impulses from left side sent to right hemisphere, integration gives distance and perspective

Controls voluntary actions, such as learning, memory, personality and conscious thought.

Receives sensory information, interprets it with respect to previous experiences Sends impulses along motor neurones to effectors to produce an appropriate response.

To control reflex activities as part of the autonomic nervous system, such as ventilation and heart rate

Main controlling region for the autonomic nervous system, one centre for parasympathetic system, one centre for sympathetic system, controls complex behaviour patterns, monitors composition of blood plasma, produces hormones

To control most of the glands in the body

Divided into anterior and posterior pituitary gland

To produce hormones such as FSH

To store and release hormones made by the hypothalamus such as ADH

Receptor detects stimulus, creates action potential for sensory neurone, sensory neurone carries impulse to motor neurone within the spinal cord via a relay neurone, motor neurone carries impulse to effector

Spinal reflex

When the neural circuit only goes up to the spinal cord, not the brain

Leg tapped just below the patella, stretches the patellar tendon, initiates the reflex arc, extensor muscle on top of the thigh contracts, relay neurone inhibits motor neurone of the flexor muscle so it relaxes, contraction of the extensor muscle causes the leg to kick

Maintaining posture and balance

Knee jerk, blinking

Cranial reflex

Blinking as a reaction to overly bright light

A reflex that occurs in the brain

Irritation of the cornea triggers an impulse along the fifth cranial nerve, passes through a relay neurone in the lower brain stem, impulses then sent along branches of the seventh cranial nerve, results in the eyelids closing

Both things respond in the same way to a stimulus

Blinking reflex

Involuntary responses so the brain can deal with more complex responses, not learnt so provide immediate protection, fast

Stimulus that causes the stress response which causes wear and tear on the body's physical or mental resources

Full range of coordinated responses of animals to situations of perceived danger

Shift in the balance of stimulation to increase activity of the sympathetic nervous system and a decrease in activity of the parasympathetic nervous system

Hypothalamus activates sympathetic nervous system and the adrenal-cortical system by releasing CRF, sympathetic nervous system activates the adrenal medulla which releases adrenaline and noradrenaline, sympathetic nervous system leads to impulses that activate glands and smooth muscles, anterior pituitary gland releases ACTH which leads to the adrenal cortex which releases hormones

Cortisol, corticosterone

To regulate metabolism and blood pressure responses to stress

Regulates immune response and suppresses inflammatory reactions

Binds to its receptor, activates inactive adenyl cyclase to make active adenyl cyclase which is an enzyme, ATP is then converted into cAMP, cAMP is the second messenger

Centre in the medulla oblongata which increases heart rate sends impulses through the sympathetic nervous system in the accelerator nerve to the SAN

Centre in the medulla oblongata which decreases heart rate sends impulses through the parasympathetic nervous system in the vagus nerve to the SAN

Chemoreceptors, baroreceptors