- Created by: Georgiaeveritt
- Created on: 06-06-19 08:52
The Nervous System
- Specialised network of cells and our primary communication system.
- Two main functions; Collect,process and respond to information and the environment, and to co-ordinate the working of differenet organs and cells in the body.
- Divided into the Central Nervous System (CNS) and Peripheral Nervous System (PNS)
Structure and functions of CNS
- Made up of the brain and spinal cord, the brain being the centre of all conscious awareness
- Spinal cord is an extension of the brain, responsible for reflex actions
- Passes messages to and from the brain and connects nerves to the PNS
Structure and functions of PNS
- Transmits messages via millions of neurons to and from the nervous system
- Subdivided into the ; autonomic nervous sytem and the somatic nervous system
- ANS- governs vital functions in the body such as breathing, heart rate, digestion
- SNS- controls muscle movement and receives info from sensory receptors.
The Endocrine System
- works alongside the nervous system to control vital functions in the body through actions of hormones
- Works much more slower than the nervous system but has powerful effects.
- Organs in the body that produce hormones
- major endocrine gland is the pituitary gland, known as the 'master gland', located in the brain.
- Secreted into the bloodstream and affect any cell in the body that has a receptor for that particular hormone
Endocrine system and the ANS work together
- Sympathetic state; increase HR, increase BR, dilated pupils, inhibits digestion etc
- Parasympathetic state; Decrease HR, decrease BR, constricts pupils, stimulates digestion.
Structure and function of neurons
There are three types of neurons;
- Motor neurons- connect the CNS to effectors (muscles and glands). They have short dendrites and long axons
- Sensory neurons- Carry messages from the PNS to the CNS. They have long dendrites and short axons
- Relay neurons- Connect sensory neurons to motor or other relay neurons. They have short dendrites and short axons.
Structure of Neurons
- Cell body (soma)- Includes a nucleus which contains the genetic makeup of the cell
- Dendrites- branch-like structures that protrude from the cell body. Carry nerve impulses
- Axon- carries electrical impulse away from the cellbody down the length of the neuron
- Myelin Sheath- Covers the axon to protect it
- Nodes of Ranvier- Gaps in the axon that speed up the transmission of the impulse
- Terminal button- end of axon, to communicate with the next neuron, across the synapse.
- When a neuron is at resting state- inside is negative, when activated it is positive.
Synapse- A tiny gap which separates each neuron
- Signals within neurons are transmitted electrically
- Signals between neurons are transmitted chemically across the synapse
- When the electrical impulse reaches the end of the neuron it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles
- Once the neurotransmitter crosses the gap it is taken up by the post-synaptic receptor
- The chemical message is coverted back into an electrical impulse and the process of electrical transmission begins
- Chemicals which diffuse across the synapse to the next neuron
Excitation and Inhibition- e.g adrenaline is excitatory and serotonin is inhibitory.