the nervous system Flashcards
neuron
excitable cell with a membrane that can generate and conduct signals/ action potentials
the body of the cell is made of a nucleus and much of the cytoplasm and they have the greatest metabolic activity
dendrite- CARRIES IMPULSE TOWARD CELL BODY
axon- CARRIES IMPULSE AWAY FROM CELL- end at axon bulb
SENSORY NEURON-carries impulse from sense organ to brain or spinal cord **long dendrite and short axon
cell body on the outside
MOTOR NEURON-carrijes impulse from brain to spinal cord to muscle or gland -SHORT DENDRITE AND LONG AXON the cell body is at one end of it and there are a bunch of dendrites branching off
INTERNEURON- connects sensory neurons to motor neurone and receive impulses from other neurones SHORT DENDRITES AND SHORT AXONS they are in the spinal cord or brain and THEY DO NOT HAVE MYELIN
gilial cells
insulate and and nourish other brain cells
neural signalling
reception- detection of stimulus- neurons and sensory receptors detect
transition- message sent along neutron then another neuron then to a muscle or a gland
INTEGRATION- sorting/ interpretation of neural messages and determine responses
response- output- action resulting from the integration of a neural message
central nervous system- spinal cord
brain and spinal cord, has three membranes called meninges and cerebrospinal fluid which cushions it. the spinal cord has two functions 1. reflex- causes skeletal and smooth muscle contractions 2. communicating brain with spinal nerves– one pair of spinal nerves leaves the spinal cord between each vertebra
spinal cord made of gray and white matter
gray matter
cell bodies are short and unmyelinated
white matter
myelinated axon bulbs
central nervous system- brain
-cerebrum- 2 hemispheres- last to receive sensory impulses and controls the voluntary response
-lobes- frontal conscious thought and personality, motor areas control skeletal muscle and motor control of speech.
-temporal lobe-smelling and hearing
-parietal lobe- sensory strip receives impulses from skin and receptors
-occipital lobe- controls vision two hemispheres bridged by CORPUS CALLOSUM – right and left share info.
-limbic system under cerebral cortex- emotions pleasure, rage, sexual interest, learning, memory
-thalamus-recieves all impulses (except smell) and channels them to cerebrum- connected to Medulla oblongata by the ascending reticular activating system
- hypothalamus- maintains homeostasis of body and controls the pituitary gland- links exocrine system with nervous system.- osmoreceptors control OP chemoreceptors detect chemical changes, temp receptors
cerebellum- second largest part of brain- controls fine muscle coordination- balance- smooth muscle
medulla oblongata- close to spinal cord- BOSS OF AUTONOMIC NERVOUS SYSTEM- coordinates heartbeat breathing rate blood pressure and reflexes
LABEL DIAGRAMS
autonomic nervous system
the response depends on where the nerve comes from
- sympathetic nervous system– thoracic and lumbar region
response-inhibit tears -dialate pupils -inhibit salvation -dilate air passage -speeds up hr -adrenal secretion -inhibit digestion -decrease intestinal activity -inhibits urine -genitals become erect -liver releases glucose (emergency situations)
parasympathetic nervous system- cranial region and sacral region
response- stimulates tears -constricts pupil -constricts bronchioles -slows heart -stimulates gal bladder to release bile -increased activity of stomach and pancreas - increase intestinal activity - stimulates urination -causes orgasmic contractions
neuron impulse transmission
the axon or dendrite fibre carries the impulse and it is made by the position of Na and K ions. for a resting potential the Na is outside the membrane and K is inside the membrane also ve negative proteins are inside the membrane. so the charge outside is positive and the charge inside negative. this means the membrane is polarized (there are nak pumps to maintain the resting potential)
once a stimulus meets threshold and action potential also known as an impulse occurs - this is an exchange of ions across a membrane– Na gates open and na diffuses in depolarizing the membrane because the inside is now positively charged and the outside is negatively charged. the flow of the electric current that affects the permeability of the adjacent area of axon and the depolarization travels down the axon or dendrite ( the na gates are open for only a fraction of a second)
then the k gates open which takes a tiny bit longer and K rushes out, this repolarizes the membrane then the refractory period occurs and the Na K pump moves Na out and K back in (the neuron can’t fire at this time)
rate of impulse conduction
unmyelinated- 2m/s
myelinated- 100-200 m/s
reflex arc
-pathway- sensory receptors detect stimulus (pain temp chemo) impulse travels down DENDRITE of SENSORY NEURON to cell body then travels from cell body to AXON of the same neuron. the impulse reaches the axon bulbs in the spinal cord where SYNAPSE occurs and the signal is transmitted to the DENDRITE of an INTERNEURON which travels down AXON and reaches another axon bulb crosses synapse and goes to DENDRITE of a MOTOR NEURON and it leaves the cell body on an AXON until it reaches a NEUROMUSCULAR JUNCTION where a response occurs
structure of reflex arc
sensory neuron leads to dorsal root ganglion which leads to spinal cord which leads to motor neuron and ventral root ganglion which leads to response
the synapse
location at which a neuron transfers impulse to another neuron (axon terminal or bulb) this is carried out by neurotransmitters which are stored in synaptic vesicles - neuron receiving impulses must INTEGRATE the incoming messages which are either excretory or inhibitory and the receiving neuron adds all these to determine the overall stimulation will cause to to develop an action potential
steps of synapse
step 1- impulse reaches end of axon terminal- gated channels for Ca ions open in the presynaptic membrane
step 2-ca in synaptic cleft diffuse into axon terminal and interact with microfilaments
step 3- microfilaments contract in the presence of ca pulling synaptic vesicles (with neurotransmitters) to presynaptic membrane vesicles fuse with membrane and Neurotransmitters are released into the cleft
step 4- ca is pumped back into cleft and neurotransmitters bind with receptors on the post synaptic membrane of the dendrite
step 5-receptors activated by neurotransmitters cause the gated Na channels of dendrite to open up this is action potential or an impulse
step 6- enzymes in the cleft destroy NT on receptors or cause them to go back to the er and get recycled
drugs
drugs cause physical addiction— the hypothalamus maintains homeostasis and monitors all substances - drugs mimmic opiates and neurotransmitters - when the levels of drugs are high the hypothalamus perceives this as the level of NT are high so the body shuts down the production of neurotransmitters and once the drug is removed from the body the user crashes - this is known as physical addiction because the user has to take the drugs to feel like the body has natural opiates of NT
