Nervous System 1 Flashcards
Describe the nervous system.
- The body’s command centre
- Electrical and chemical communication occurs throughout the body
State the two main parts of the nervous system.
- Central Nervous System
- Peripheral Nervous System
What is involved in the CNS?
Brain and Spinal chord
What is involved in the peripheral nervous system?
Afferent Nerves: sensory neurons - messages from periphery to spinal chord
Efferent Nerves: Motor neurons - messages from spinal chord to muscle/glands
State the divisions of the peripheral nervous system
CNS - Sensory division (afferent) and motor division (efferent)
Motor division - Autonomic Nervous System and Somatic Nervous system
Autonomic Nervous System - sympathetic division and parasympathetic division
What are the building blocks of the nervous system?
- Neuron
- Oligodendrocytes (CNS)/Schwann cells (PNS)
- Astrocytes
- Microglia
Describe neurons.
Electrically excitable cell that receives, processes and transmits information through electrical and chemical signals.
Describe oligodendrocytes (CNS)/Schwann cells (PNS)
- Produce myelin
- Facilitate transmission
Describe astrocytes
- Enables homeostasis
- Physical barrier/connector
- Reputake of neurotransmitters
- Support neurons
Describe microglia
- Immune cells of the brain
- Phagocytose dead cells and debris
Describe the structure of neurons.
- Cell body (soma): control centre
- Dendrite: short, branched extension of a nerve cell where impulses received from other cells at the synapses and transmitted to the cell body
- Axons: originate at axonal hillock and allows material to be transported from cell body to axon terminal
- Synapse: Where axon terminal meets target cell
Describe the signals of the neurons.
PNS - afferent or sensory neurons signals from the periphery to CNS
Efferent neurons - motor neurons signals from CNS to the muscle/skin
CNS - Interneurons connecting brain and spinal chord
Define nerve.
- A bundle of fibres that conduct impulses between the brain and spinal chord and another part of the body
- Nerves include fragments of neurons (axons) and non-neuronal cells (neuroglia)
What is the membrane potential?
The difference in electrical charge between the inside and the outside of the neuron
- is a result of ion gradients
What are excitable cells?
Membrane potential changes in response to stimuli e.g. neurons
What are nerve impulses?
Changes in membrane potential that travel down nerves
Describe the features of the cell membrane.
- Highly impermeable to ions
- Allows electrical signalling and excitability
State the types of transport across cell membranes.
- Passive diffusion
- Facilitated diffusion
- Active transport
- Secretory/endocytic pathways
Describe the membrane potential of neurones?
- It is more negative on the inside than the outside of the cell
- Membrane potential is due to unequal ion distribution
- A gradient of ions across the membrane provides the membrane potential
How do action potentials travel in neurones?
Travel one way - from dendrites to axons
How does an action potential changes the membrane?
Changes it to +30mV
How are electrical impulses formed?
By ions moving into the neruon
How is the axonal action potential made up of?
Movement in sodium (+ charged ion) and potassium (+ charged ion)
What does the signal received at dendrites cause?
- Causes dendritic depolarisation: ligand gated ion channels and metabotropic receptors
- This depolarisation opens voltage gated sodium channels
What is the stimulus?
It can be electrical mechanical or chemical.
Describe the all or nothing principle.
- Stimulus has to be strong enough to reach threshold potential
- Enough depolarisation to open first Na channels
- Sodium channels in the membrane are sensitive to voltage and open when the threshold membrane potential is reached
Describe action potential propagation.
- The action potential Is propagated down the axon by voltage sensitive channels
- Na+ voltage sensitive channels open due to local change in membrane potential
- Causes more Na+ channels to open
- Na+ channels behind the action potential become inactive
- This means action potential can only move in ONE direction.
Describe a synapse.
When one neurone meets another
Describe how neurones form networks and communicate.
- Electrical action potential triggers release of chemical signal (neurotransmitter)
- Neurotransmitters from the pre-synapse bind to postsynaptic receptors
- This triggers depolarisation of the postsynpatic neurone
What are the two ways synapses can be described?
Excitatory - stimulus in second neurone
Inhibitory - Stimulus in 1st make an AP less likely to occur
What is summation?
The combination of graded potentials in the post-synaptic neurone.
State and describe the structures of the brain.
Cerebrum - Higher functions
Brain Stem - Involuntary functions, blood pressure, breathing, vomiting, sleep/arousal - includes the midbrain, pons and medulla
Cerebellum - co-ordinates balance and movement
Diencephalon - Homeostasis - its between brain stem and cerebrum and includes thalamus, hypothalamus and pineal gland.
Describe the cerebrum: cortex.
- 2 hemispheres joined by corpus callosum
- Surface folded
- Frontal: reasoning, planning, speech,
movement, problem solving - Parietal: movement / orientation
recognition, sensory information (pain) - Occipital: visual processing
- Temporal: perceptions/recognition of
auditory stimuli
Describe the cerebrum: sub-cortical structures.
- Basal ganglia: motor control
- Limbic system:
- Amygdala: emotion and memory
- Hippocampus: Learning and memory
(under temporal lobe) - Pituitary gland: a small gland located at the base of the brain below the hypothalamus - growth
hormone, TSH
State the four regions of the spinal chord.
- Cervical
- Thoracic
- Lumbar
- Sacral
Describe the function of the spinal cord.
- Connects your brain to your lower
back - Carries nerve signals from your
brain to your body and vice versa - Spinal cord is where information
comes into the CNS and
directions are sent out
What is the distinct pattern of the spinal cord.
- Sensory nerves enter via dorsal root
- Motor nerves leave via ventral root
Describe the spinal cord peripheral nerves.
(branches off
from spinal cord).
Spinal nerve: a mixed spinal nerve, which carries motor, sensory, between the spinal cord and the body.
Paired peripheral nerves that arise from the spinal cord.
In humans there are 31 pairs:
8 cervical,
12 thoracic,
5 lumbar,
5 sacral, and
1 coccygeal.
Each pair connects the spinal
cord with a specific region of the body.
