nervous system Flashcards
what is the nervous system responsible for
coordination of activities in the body… allows animal to respond to internal + external changes called stimuli
name the two parts the nervous system is divided into and name these giving an example of what each consists of
CNS- central nervous system consists of brain + spinal cord
PNS - peripheral nervous system consists of a vast network of nerves that carry messages between the CNS + rest of the body
name + describe the 4 processes involved in making a response to a stimulus
Reception: stimulus detected by neurons + nerve cells
Transmission: message passes along neurons in the PNS from receptors to the CNS, and then to effectors e.g muscles.
Integration: incoming messages are sorted, processed + response is decided upon… happens in the CNS, especially the brain
Response: carried out by effectors e.g muscles/glands when they are stimulated by neurons
define neuron
nerve cell… basic units of the nervous system
there are three types of neurons, name + describe each type
Sensory (afferent) neurons take messages from sense organs to the CNS
Motor (efferent) take messages from the CNS to muscles + glands causing them to respond
Interneurons: short neurons not enclsoed in a myelin sheath that carry information between sensory + motor neurons. found only in the CNS
define receptor
a group of cells that detect a stimulus
what is a nerve ending
connects sensory neurons to receptor cells or sensory organs
what is a dendrite
a fibre that carries impulses towards the cell body
what is an axon
carries impulses away from cell bodies
define Schwann cells and state where they are found
located along the length of neurons, make the myelin sheath
what is the myelin sheath
fat rich membrane that insulates electrical impulses
what is a ganglion
a group of cell bodies located outside the CNS
where are the cell bodies of sensory neurons found
outside the CNS
where are the cell bodies of motor neurons found
within the CNS
draw a labelled diagram of a sensory and motor neurons
draw a labelled diagram of an interneuron
what are neurotransmitter swellings and where are they found
ends of each axon breaks into many axon terminals. these small branches end in a swelling called a neurotransmitter swelling. these release chemicals that carry the impulse from one nerve cell to another. the chemicals are neurotransmitters and are stored in vesicles in the swellings
describe how nerve impulses are transmitted
a neuron receives a stimulus of sufficient strength (above the threshold). an impulse travels along the dendrite and axon to the neurotransmitter swellings. this movement involves the movement of ions (H+, K+, Na+). if the threshold isnt reached, nothing happens
what is the all or nothing rule
the the threshold is reached an impulse is carried. if the threshold is not reached, no impulse is carried
describe the terms threshold
the minimun stimulus needed to cause an impulse to be carried
what is a resting neuron
when a neuron is not carrying an impulse ions are pumped in and out of the axon. this results in a negative inside and a positive outside in the axon
describe the movement of impulse
once the threshold is reached the axon/dendron changes its permeability to ions. the inside of the axon becomes positive, outside is negative at the site of stimulation. this causes the next section to alter its permebility in a similar way. a chain reaction is set up. a movement of positive charge moves along the inside of the axon. ATP is needed to cause these changes . once the impulse has moved along, the area behind is restored to the resting state
describe the refractory period
a short timespan after a neuron has carried an impulse during which a stimulus fails to cause a response (motor neuron hasnt send the impulse to the effectors)
what is meant by the speed of an impulse
the speed at which an electrical impulse travels along a neuron
what factors affect the speed of an impulse
whether myelin is present/absent - 2m/s if absent, 120m/s if present. diameter f the axon/dendrite, larger the diameter, faster the impulse
what is a synapse
a region where two neurons come into close contact, commonly found between the axon terminals of one neuron and the dendrites of another
what is a synaptic cleft
tiny gap between the two neurons at a synapse
draw a labelled diagram of a synapse
explain how neurotransmitters are activated
electrical impulses cannot cross a synapse. ions stimulate the neurotransmitter swellings in the presynaptic neuron to release a chemical (neurotransmitter) that diffuses rapidly across the synaptic cleft and combines with receptors on the post synaptic neuron. this causes the electrical impulse to be regenerated
where are neurotransmitters made + give an example
some are made in cell bodies of neurons, others are made in neurostransmitter swellings. over 60 are known, e.g ACh and dopamine
how are neurotransmitters inactivated
it is broken down by enzymes and the digested neurotransmitters re reabsorbed back into the neurotransmitter swellings where they can be recycled
give 4 functions of synapses
transmit impulses from one neuron to another to an effector.
they control the direction of the impulse
they prevent overstmulation of effectors
the impulse can be blocked by certain chemicals (drugs/nerve blocks)
what part of the nervous system does the brain belong to
central nervous system
explain the function of the brain
acts as an interpreting centre to sort and process incoming impulses and decides a response
describe the structure of the brain
composed of 12,000 million neurons. has grey matter (cell bodies + synapses) and white matter (nerve fibres aka dendrites and axons). brain uses 20% of the body’s energy
how are the brain + spinal chord protected
bone covered in three membranes called meninges. the space between the inner two meniniges is filled with cerebrospinal fluid which acts as a shock absorber and as an exchange medium between the blood + brain
what is the largest part of the brain, describe its structure and functions
cerebrum, contains 75% of neurons in hte brain
it is divided into the left + right cerebral hemispheres.
outer part is called the cerebral cortex and is grey
innter part has white matter and has millions of nerve fibres tha connect different areas of the cortex and two sides of the brains
functions include: controlling voluntary movement, recieving and interpreting impulses, thinking, memory, emotions
-> the right hemisphere controls the left side of the body and the left hemisphere controls the right side of the body
what is the second largest part of the brain,describe structure + functions
cerebellum, heavily folded, controls muscular coordination, allows smooth, refined muscular action and controls balance. responses are involuntary (not conciously controlled)
what is the medulla oblongata
connects the spinal chord with the rest of the brain. contain clusters of nerve cells that control involuntayr actions such as breathing (detects co2 concentration), blood pressure, sneezing, coughing
describe the thalamus and hypothalamus
thalamus: located below the cerebrum + relays all incoming messages to relevant parts of the brain.
hypothalamus: lies below the thalalmus and regulates internal environment of the body (homeostasis). links the pituitary gland to regulate hormone production
label the regions of the brain with the senses they control
describe a nervous system disorder, causes, symptoms, prevention + treatment
parkinson’s disease
cause: failure to produce neurotransmitter dopamine resulting in inability to control muscle coordination
symptoms: trembling of hands/legs, muscles become stiff + rigid
prevention: no known way
treatment: physio, special exercises, treatment with drugs to stimulate dopamine- can all help but not stop degredation of the brain
what does the spinal chord consist of + what is its function
composed of nerve tissues. surrounded by bony vertebrate that protect it. transmits impulses to and from the brain + controls many reflex action
where is the spinal cord located + what does it look like
located in the neutral canal of the vertebrae. appears as an outer ring of white matter (axons only) surrounding an inner H shape region of grey matter (cell bodies + dendrites). at the centre is the central canal containing cerebrospinal fluid
distinguish between grey + white matter in the spinal cord
white matter = axons only, inner H shape grey matter( cell bodies and dendrites). centre of grey matter is central canal with cerebrospinal fluid
distinguish between ventral + dorsal roots
dorsal root carries sensory neurons into the spinal cord. ventral root carries motor neurons out
draw a labelled diagram of a TS of the spinal cord
what are the swellings in the dorsal root called
ganglia
what does the PNS consist of
nerve fibres outside the brain + spinal cord. made up of long dendrites or axons taking impulses to or from the CNS. cell bodies of sensory nerves are located in the ganglia in the PNS
what is a reflex action
an automatic, involuntary response to a stimulus
what is a reflex arc
the neurons forming the pathway taken by nerve impulses in a reflex action make up a reflex arc. these are the unit of function of the nervous system
give examples of reflex actions
grasp reflex, movement of the iris in the eye, breathing, blinking
what is the function of a reflex action
fast responses to protect the body from damage
describe the mechanism of a withdrawl reflex
receptors in the fingers are stimulated by a hot flame, sensory neurons carry an impulse into the spinal cord. neurmerous synapses are made with other neurons. an interneuron carries the impulse to the brain, motor neurons take the impulse straight out of the spine to the effector, causing us to pull our hand back from the flame
draw a labelled diagram of a reflex arc
are neurotransmitters carried in the blood
no
give two ways a nervous system response differs from a hormonal response
nervous = fast, hormonal = slow. nervous = electrical, hormonal = chemical
name the type of particle whose movement in and out of neurons is an essential feature of a nerve impulse
ion
how is a neuron adapted to carry impulses
insulated, has axons, dendrites and neurotransmitters
draw a labelled diagram of a neuron including axons, dendrites and myelin sheath
