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Responding and Controlling - Coggle Diagram
Responding and Controlling
Communication:
Nerves
A
nerve
contains a bundle of nerve cells called
Neurons
Neurons carry electrochemical messages called
impulses
throughout the body.
Nerves can vary in length from 1mm to over a metre
Neurons
A neuron consists of:
Cell body: Contains nucleus & most of the cytoplasm
Dendrites: Projections that bring impulses into the neuron to the cell body.
Axon: Long projection that carries impulses away from cell body towards next neuron
Myelin sheath: Protective white fatty tissue
There are three main neurons in the body:
Sensory- Carry impulses from sense organs to spinal cord and brain
Interneuron- Processes impulses in brain and spinal cord
Relay impulses from sensory neurons to appropriate motor neurons
Motor neuron- Carry impulses from the brain & spinal cord to effectors (muscles & glands)
Nerve generation & transmission
Nerve cells contain positively charged ions (sodium and potassium) and negatively charged protein molecules.
When stimulated they become electrically excited and generate an impulse.
An impulse begins when one neuron is stimulated by another neuron or by the sense organs.
The impulse travels down the axons of sensory neurons to the nerve cells in the brain called interneurons.
The brain will then send an impulse through motor neurons to the necessary muscle or organs, telling it to contract
Impulses in a neuron
Synapses-
Because neurons never touch, chemical signalers called neurotransmitters must travel through the space called synapse between two neurons.
Receptors
Receptors are groups of specialised cells that can detect changes in the environment called stimuli.
Chemoreceptors: Chemicals in smell, taste and concentration of CO2, and O2 in blood.
Mechanoreceptors: Physical stimuli such as pressure, touch, tension, sound vibrations, balance.
e.g. insects can detect airborne vibrations 3.6km away
Photoreceptors: Light in retina of eyes and cells in body surfaces
Thermoreceptors: Hot and cold, in skin and hypothalamus of brain e.g. pythons have thermoreceptors in their lips to help detect prey.
Pain receptors: free nerve endings in skin
The Nervous System
A communication system that controls and coordinates functions throughout the body and responds to internal and external stimuli.
Central nervous system:
Spinal Cord-
The main communications link between the brain and the rest of the body
Brain The brain consists of three main areas which contain several lobes:
1.Cerebrum-
Voluntary or conscious activities of the body-learning, judgment
Frontal lobe:
Planning, reasoning/judgement, movement and some aspects of speech.
Parietal lobe:
Touch and sensation information of heat cold, pressure and pain.
Occipital lobe:
Information from the eyes.
Temporal lobe:
Hearing, speech and some kinds of memory
3.Brain stem (Medulla oblongata)-
Controls involuntary actions like blood pressure, heart rate, breathing, and swallowing
Essential survival functions; heart rate and breathing.
2. Cerebellum
Coordinates and balances the actions of the muscles
Posture, balance and coordination
Takes over some learned motor skills from cerebrum like tying shoelaces and bike riding.
Peripheral nervous system:
Sends impulses AWAY from the CNS to effector organs.
Nerves & Sense Organs
Somatic Nervous system:
Sends messages to skeletal muscle (voluntary nervous system)
The somatic division consists of:
Sensory neurons which carry nerve impulses from sense and internal organs towards CNS.
Motor neurons which carry nerve impulses away from the CNS to effectors.
Autonomic nervous system:
Sends messages to smooth muscle, heart muscle, glands (Involuntary NS)
Consists of two divisions
Sympathetic Division
Increased Metabolic rate
Heart muscles contract faster
FIGHT or FLIGHT repsonse
Sympathetic division is still active on a regular basis for the maintenance of homeostasis.
Parasympathetic Division
‘Rest and Digest’
Bodily functions when we are relaxed
Reduced metabolic rate
Overall, these regulate the internal environment of an individual
Reflex Arc
A reflex is an involuntary response that is processed in the spinal cord not the brain.
Reflexes protect the body before the brain knows what is going on.
Reflex action: Standing on a tack
1.Skin receptors on foot feel prick of the tack
2.Nerve impulse travels along the sensory neuron up the leg to the CNS spinal cord.
3.Nerve impulse received at the spinal cord, acting as the interneuron.
Nerve impulse leaves interneuron (spinal cord) and travels along the axon to the leg muscle (motor neuron) away from the CNS towards the effector.
5.The muscles in the leg (effector) acts to remove the foot from the initial stimulus.
