central nervous system Flashcards
what is the CNS composed of. what is its role.
the brain, spinal cord, sensory organs, nerves. information is evaluated and decisions are made.
what is the peripheral nervous system
Sense cells such as skin. Able to detect changes in the external environment. Send electrical impulses along the sensory neurones to the CNS to bring about a response.
what are neurons and the 3 classes.
nerve cells that communicate within the body. sensory neurons transmit sensory signals to the CNS from receptors to the body. motor neurons transmit signals from CNS to effectors in the body ie muscles and glands. Relay neurones carry electrical impulses between sensory neurones, the brain and the brain and motor neurones (country lanes)
What are Schwann cells
They produce fatty acids which allow the electrical impulse to jump across myelin sheath cells by saltitory conduction for faster transmission.
Describe three ways in which the CNS is protected
Brain and spinal cord are covered in mengines (protective membrane). The brain is protected by the skull. Cerebrospinal fluid acts as a buffer between brain and spinal cord (electrical impulse).
what is the somatic nervous system
voluntary/ conscious movements and the reflex arc which doesn’t require going to the brain to bring around a response to change in external conditions
what is the autonomic nervous system
the PNS includes all the involuntary efferent neurons. sympathetic - flight to fight response to stress, danger, excitement. increase heart rate, respiration and breathing rate. releases nor adrenaline and adrenaline from the adrenal medulla. parasympathetic- decreases heart rate and breathing rate, increases digestion ie feeling relaxed and at rest.
how do neurons function
generation of an action potential when Na+ and K+ ions move through the membrane of neurones. At rest the conc of Na and K is the same outside and inside of the cell the overall charge however is negative. depolarisation is when Na carries a positive charge into the cell so it because positively charged and is more likely to fire. repolarisation is when K ions diffuse out of the neuron so the resting membrane potential is restored and less likely to fire.
