Nervous system Flashcards
Human nervous system
Network of nerve cells and fibres which transmits nerve impulses between parts of the body.
It receives and processes sensory information from the environment, and transmits motor information around the body, that, in turn determines our reaction to environmental stimuli.
Divisions of the nervous system.
1) Central Nervous System
2) Peripheral Nervous System
Central Nervous System
Role of the brain and spinal cord
Composed of the brain and spinal cord.
The brain receives and processes information and co-ordinates a response.
The spinal cord connects the brain to the rest of the body. It sends information from the sensory neurons in various parts of the body to the brain and it relays motor commands back to muscles and organs via motor neurons.
Peripheral Nervous System
Peripheral NS is connected to the spinal cord and consists of all the nerves outside the Central NS
It carries sensory information from the body to the Central NS and motor information from the Central NS to the body.
Consists of the Somatic NS and Autonomic NS.
Somatic Nervous system
Transmits sensory information to the Central NS and carries out its motor commands
Involved with voluntary muscle movements
Autonomic Nervous system
Carries information between the central NS and internal bodily structures (heart, lungs, glands) that carry out basic life processes
Divided into sympathetic and parasympathetic
Sympathetic Nervous System
Readies the body for the fight, flight or freeze response when its exposed to threats.
E.G Stops digestion, increases heart rate, dilates pupils, diverts bloody away from the stomach to the muscles
Parasympathetic Nervous System
Supports more mundane, or routine activities, that maintain the body’s store of energy (e.g regulating blood sugar levels, secreting saliva)
When the threat has passed the parasympathetic NS resumes control from the sympathetic NS
E.G heart rate lowers, blood pressure lowers, pupils constrict, stop sweating, digestion increases, bladder control
Types of neurons
Sensory / afferent neurons: Transmits information from the sensory cells in the body to the brain. (Peripheral NS)
Interneurons: Provide links between the sensory neurons and motor neurons (organises and integrates) (Central NS)
Motor / efferent neurons: Transmits commands from the interneurons to the glands, organs and muscles of the body
Anatomy of a neuron:
Dendrites role:
Receive input from other neurons.
Anatomy of a neuron:
Cell body / soma role:
Includes a nucleus which controls the neuron.
Anatomy of a neuron:
Axon role:
Transmits information to the other neurons.
Anatomy of a neuron:
Myelin Sheath:
“Fatty covering” that insulates the axon from chemical and physical stimuli that might interfere with the transmissions of nerve impulses. Speeds up neural transmissions.
Anatomy of a neuron:
Axon terminals role:
Allow for the branching out of the axon which contain synaptic knobs at the end of terminal.
Anatomy of a neuron:
Synaptic knobs role:
Contains vesicles which hold neurotransmitters involved in moving signals to the adjacent cells.
Anatomy of a neuron:
Synapse role:
The space between neurons where transmission occurs.
What are the function of glial cells?
Provide the structural framework that enable a network of neurons to remain connected.
Supply nutrients and oxygen to neurons so they can function
Destroy and remove dead neurons
Soak up excess neurotransmitters at the synapse that can clog the communication between neurons.
Block the entrance of toxic barriers to the brain.
Types of Glial cells:
Hint: AMOS -SS
Central NS:
Astrocytes, microglia, oligodendroglia
Peripheral NS:
Satellite cells, schwann cells
Stages of neural communication
Resting potential, threshold, depolarisation (action potential), repolarisation
What is resting potential
The neuron is not sending an electrical signal
The inside of the neuron is negative (relative to the outside) otherwise known as polarised
There a re more “positive” sodium ions outside the cell and more “negative” potassium ions inside the cell
The voltage inside the cell is -70mV
Sodium outside, potassium inside. Positive outside, negative inside
What is threshold
An event (stimulus) causes the resting potential to move toward 0mV. Neurotransmitters bind with receptors at dendrites, this increases the charge of the cell. When the charge reaches -55mV this causes sodium channels to open. When the threshold is reached an action potential will always fire
(If neuron does not reach this critical threshold level, then no action potential will fire) ( All or nothing event)
What is depolarisation (Action potential)
After the threshold has been reached depolarisation occurs. This is when positively charged sodium ions rush into the cell via sodium channels causing the cell to become positive.
Inside the cell rushes to +40mV (action potential)
This process is called depolarisation because cell which was polarised now reverses that polarisation
Process only occurs in one section of a cell at a time before triggering the adjacent section, this movement of a positive charge along the axon is called an impulse.
What is repolarisation
After the action potential has occurred, the cell returns to its resting state.
Potassium channels open, potassium rushes out of the cell, reversing the depolarisation (repolarisation)
This starts to make the cell more negative so that it returns to resting potential.
Then sodium pumps remove the sodium and the cell eventually returns to resting potential.
The neural impulse (action potential) continues to travel along the axon until it reaches the terminal button.
What is the lock and key process
Receptor sites are specifically designed to only bind with certain neurotransmitters. Their characteristic pattern allows them to match the pattern of the neurotransmitter like a lock matches a key. The receptor site has a complementary structure to the neurotransmitter.
What effects do neurotransmitters have
Excitatory: they excite the post synaptic neuron to fire
Inhibitory: They inhibit the post synaptic neuron from firing
What are the regions of the brain
Hindbrain, midbrain, forebrain
What is the cerebal cortex
The largest region of brain and plays a key role in memory, attention, perception, cognition, awareness, thought, language and consciousness.
The cerebral cortex is…
Convoluted (folded) - allows for greater surface area (0.25m squared) compared to volume
Divided into 2 halves called hemisphere
What is the function of the cerebral cortex
Receiving and processing sensory information
Initiating motor responses
Contralateral organisation:
Right hemisphere receives sensory info from the left hand side of the body and controls movements on left hand side of body
What is gyri
The elevation points of the brain
What is sulci
The folds or groove that seperate gyri
Longitudinal fissure
Separates the 2 hemispheres in the cerebral cortex
Specialised functions of the left hemisphere
Verbal functions: speaking, reading, writing
Analytical functions: Logical reasoning, critical evaluation
Non verbal: sensory and motor functions from the right hand side of the body
Specialised functions of the right hemisphere
Spatial and visual thinking: jigsaws, recognising faces, creativity
Recognition of emotions relating to facial expressions
Sensory and motor functions from the left hand side of the body
Corpus Callosum
Bridge of nerve tissue that connects the two cerebral hemispheres
Allows for communication between the two hemispheres
