The Central Nervous system Flashcards
What are the 2 parts of the nervous system?
-Central (brain & spinal cord)
-peripheral (All of the nerves coming out of the spinal cord)
What does the central nervous system do?
-integrates sensory information
-coordinates conscious and unconscious activity
What does the spinal cord do?
main pathway for movement of information between brain and peripheral nervous system
-Contains neural networks responsible for movement
and spinal reflexes
what are the 4 parts of the brain?
-cerebellum
-brain stem
-cerebrum
-diencephalon
What does the cerebellum do?
-Helps coordinate muscle activity and voluntary movements
-helps maintain balance and posture
What does the brain stem do?
-plays vital role in relaying information between the body and higher brain regions
What are the 3 main components of the brain and what do they do?
-Medulla oblongata-controls involuntary functions
-Pons-relay station between cerebellum and cerebrum and controls breathing
-Midbrain-controls eye movement
What does the diencephalon do?
-contains hypothalamus, thalamus and epithalamus
-thalamus-Rely station for sensory
information from lower parts
of the CNS
Hypothalamus- The centre for homeostasis
What does the cerebrum do?
-is the largest region of the brain- allows the increase of SA in the brain
-made up of grey(outer) matter- responsible for thinking
-and white (inner) matter-sends out signals
What is the cerebrum split into?
-is divided into the left and right hemispheres
-Each hemisphere further subdivides into a frontal, parietal, occipital, and temporal lobe.
What are the 4 lobes of the brain each responsible for?
-frontal- governs muscle movement, motor skills and cognitive function
-Parietal- processes sensory information, pain and pressure
-Occipital-vision
-temporal lobe- hearing
What is the peripheral nervous system split into?
-Afferent neurons
-Efferent neurons
What do afferent nerves do?
-(sensory nerves) send signals from senses, skin, muscles and internal organs to CNS
what do efferent nerves do?
-(motor nerves) transmit commands from CNS to muscles, glands and organs
What can efferent nerves be divided into?
-the somatic nervous system
-the autonomic nervous system
Describe the somatic nervous system?
-consists of 1 single neuron going from CNS to effector organs
-covered in myelinated sheath
-Neurotransmitter at effector is ACh
-Effector organ is skeletal muscle
Describe the autonomic nervous system?
-has divergence -one small actions can have different results(will always split-has one nerve going to the periphery which then goes to a different nerve then carries out another action)
-Effector organ is smooth muscle, gut and cardiac muscle
What is the autonomic nervous system split into?
-parasympathetic-rest and digest
-sympathetic-fight or flight
What are afferent nerves split into
-special senses (hear,smell,taste)
-somatic senses (are conscious-touch, pain, heat, itch)
-visceral stimuli (central organs-unconscious eg.heart, blood pressure)
What do reflexes do?
-they use information from joint movement, muscle tension and length and pass it through to CNS which then leads to an action taking place
-efferent motor neurons always lead to contraction
How does relaxation occur?
-caused by a reduced firing rate of a motor neuron
Give examples of 2 simple muscle contractions?
-muscle spindle reflex (load is added to muscle so muscle and muscle spindle stretch as arm extends. A reflex contractions initiated by muscle spindle and restores arm position
-golgi tendon reflex (protects muscle from excessively heavy loads-if load gets too heavy a reflex is sent out causing relaxation of the muscle and the load is dropped)
Give an example of a complex muscle contraction?
Eg.stepping on lego brick
-painful stimulus activates nociceptor
-primary sensory neuron enters spinal cord and diverges
-one collateral activates ascending pathways for sensation and postural adjustment
-withdrawal reflex pulls foot away from painful stimulus
-crossed extensor reflex supports body as weight shifts away from painful stimulus
Explain the process of control of a voluntary movement?
-sensory input from afferent neurons (goes from periphery up spinal cord to motor senses)
-within motor areas planning and decision making takes place
-then sent through to cerebellum for coordination and timing
-execution takes place as it passes along corticospinal tract to skeletal muscles
-continious feedback takes place throughout incase need to change/ alter response
What are neurons and what do they do?
-They are excitable tissue that can propagate electrical signals in response to stimuli
-They carry electrical signals
Describe the structure of a neuron?
(look at photo)
-cell body with nucleus
-dendrons and dendrites (receive info from other neurons and transfer it to cell body
-axons (carry signal away from cell body)
Describe how electrical signals are generated?
-cells in body contain cytoplasm and outside the cells there is extracellular fluid surrounding it
-cytoplasm and extracellular fluid contain dissolved ions
-ions either have positive or negative charge
-between extracellular fluid and cytoplasm positive and negative ions are not balanced
-to create signal positive ions are moved from extracellular fluid to cytoplasm (depolarisation)
-when positive ions move from cytoplasm back to extracellular fluid it becomes more negative (hyperpolarisation)
How is the movement of ions to generate electrical signals controlled?
-the membrane contains gated ion channels which open in response to stimuli allowing ions to move thru
What circumstances could cause the gated ion channels in a membrane to open?
-mechanical stimulus opens mechanically gated channel
-change in membrane potential opens bolted gated channels
-a chemical stimulus opens a ligand gated channel
What are graded potentials?
-depolarisations or hyperpolarisations that occur in dendrites and cell bodies
-they decrease in strength as it travels thru the cell body
-if remains strong enough it results in an action potential
What is an action potential?
-how we send electrical signals by travelling the length of the nerve
-caused by the change in balance between sodium and potassium (depolarisation of resting neuron)
describe how an action potential is generated?
1-neuron at resting state (all gates closed, more - charged inside (+potassium and - proteins), more + charged outside (+ sodium)
2-environmental stimulus occurs causing sodium channel to open, increasing charge in membrane (stimulus has to be strong enough otherwise action potential doesn’t take place)
3-depolarization- voltage gated sodium channels open and all sodium ions move in (signal travels)
4-repolarization- potassium ions flow out to rebalance
5-hyperpolarization-all gates close and neuron is taken back to resting state
difference between grated and action potential?
-Graded potentials - variable-strength signals that can be conveyed over small distances
- action potentials - strong depolarizations that can be transferred over long distances.
what does the cerebral cortex do?
responsible for the higher-level processes of the human brain, including language, memory, reasoning, thought, learning, decision-making, emotion, intelligence and personality
