coordination

the interlinking of activities of a living being as per the needs of the body internally or externally.

nervous coordination

it is brought about by the nervous system

which part of the body control nervous coordination

the brain, spinal cord, nerves, and sense organs

chemical coordination

it is brought about by chemical messengers called hormones.

functions of the nervous system

1. It helps keep us informed of the outside world. 2. It handles thinking, storage of memories, and reasoning 3. It regulates involuntary actions like breathing and the beating of the heart 4. It controls and harmonises all voluntary actions

what is the nervous system made of

special cells called neurons or nerve cells

what are the branches at the end of an axon called

terminal branches

what are dendrites

they are cytoplasmic extensions of the cell body.

kinds of neurons

1. Sensory neuron 2. Motor neuron 3. Association neurons

sensory neurons

carries impulses from the sense organs to the brain or spinal cord

motor neurons

carries impulses from the brain or spinal cord to the muscles or glands

association neurons

transmits impulses from one neuron to another

how do neurons communicate

Neurons do not actually touch to communicate; instead, they communicate via synapses, where the axon terminal of one cell impinges on the dendrites of another cell.

synapse

it is a small junction used for the communication of 2 neurons

why does the transmission of impulses from one neuron to another happen

it happens because of the secretion of a special chemical called a neurotransmitter.

nerve

it is formed of a bundle of nerve cells enclose in a tubular medullary sheath.

what is the purpose of the medullary sheath over neurons in a nerve

it acts like insulation and prevents mixing of impulses in adjacent fibres.

sensory nerve

contains only sensory neurons. ex: the optical nerve of the eye

motor nerve

contains only motor neurons. ex: nerves going to the muscles of the eyeball

mixed nerve

contains both sensory and motor neurons. ex: the nerves going to the tongue.

central nervous system [CNS]

It consists of the brain and spinal cord, both protected by bone.

peripheral nervous system [PNS]

it consists of nerves spreading throughout the body. it is divided into 2 parts : 1. somatic nervous system 2. autonomic nervous system

parts of the brain

1. cerebrum 2. cerebellum 3. medulla oblongata

cerebrum

it is the largest portion of the brain. it is the seat of consciousness, intelligence, and willpower. it controls all voluntary action.

what is it divided into

the cerebrum is divided into cerebral hemispheres.

grey matter

the outer portion of the cerebrum containing cell bodies of the neurons is called grey matter

white matter

the inner portion of the cerebrum containing axons is called white matter

cerebellum

it is located under the cerebrum and is much smaller. it controls balance of the body and coordination of muscular activity.

which part of the brain is affected by alcohol

The cerebellum is affected by alcohol; this is why drunk people cannot walk in a straight line and coordinate muscular movements properly.

how do the cerebrum and cerebellum work together

the cerebrum decides an action and the cerebrum coordinates and implements it.

medulla oblongata

It is the lowest part of the brain, and it connects to the spinal cord. It controls all involuntary actions. Injury to the medulla oblongata can be fatal.

grey matter of spinal cord

it is made up of cell bodies inside the inner part of the spinal cord.

white matter of spinal cord

it is made up of the axons in the outer part of the spinal cord.

functions of the spinal cord

1. the spinal cord coordinates reflexes below the neck 2. conducts messages from the skin and muscles to the brain 3. conducts commands from the brain to the muscles of the torso and limbs

somatic nervous system

it consists of two sets of nerves ; cranial and spinal nerves

cranial nerves

they emerge from the brain. there are 12 sets of cranial nerves

sensory cranial nerves

olfactory, optical, and auditory

motor cranial nerves

the nerves going to the eye muscles

mixed cranial nerves

the nerves connecting to the tongue and face

spinal nerves

they arise from the spinal cord and have 31 pairs

typical spinal nerve

mixed nerve

components of spinal nerve pair

A sensory nerve carries messages from the sense organs to the brain or spinal cord, and a motor neuron carries messages from the brain or spinal cord to the effector organs.

autonomic nervous system

it consists of a pair of nerves and ganglia found on either side of the backbone. it controls involuntary actons of internal organs.

ganglia

it is a mass of the cytons of nerve cells

kinds of autonomic systems

sympathetic and parasympathetic systems

actions controlled by the sympathetic system

1. dilation of pupils 2. constriction of blood vessels 3. acceleration of heart rate

actions controlled by the parasympathetic system

1. constriction of pupils 2. dilation of blood vessels 3. slowing down of heart rate

example of involuntary actions

tearing up of eyes when dust enters and instantaneous withdrawal of hand when it comes in contact with a hot surface

reflex action

it is a quick, immediate and automatic response to a stimulus without involvement of the brain controlled by the spinal cord.

reflex arc

the shortest pathway of the nerve impulse from a receptor to an effector which makes a reflex possible.

types of reflexes

natural/inborn reflexes and conditioned reflexes

natural/inborn reflexex

reflexes in which no prior experience is required. there are 2 kinds: protective reflexes and functional efficiency

protective reflexes

blinking, coughing, sneezes, puking

functional efficiency

peristalsis, swallowing, salivation

conditioned reflexes

reflexes developed during a person's lifetime through experience. ex: salivation upon seeing a favourite food item, typing on a keyboard, playing an instrument.

stimulus

any change in the environment that results in change of the activity of the body

response

activity of a body caused by stimulus

receptors

sense organs receiving stimulus

effectors

the muscle or gland where the response happens.

impulse

a wave of electrical disturbance that runs through the nerves