The Human Nervous System

What does the Human Nervous System consist of?

• Central nervous system (CNS) – the brain and spinal cord

• Peripheral nervous system (PNS) – all of the nerves in the body

how is info sent in the nervous system?

• Information is sent through the nervous system as electrical impulses – electrical signals that pass along nerve cells known as neurones

what is a bundle of neurones

A nerve

where does info from receptors pass on to ?

Information from receptors passes along neurones as electrical impulses to the central nervous system (CNS)

what do receptors detect?

stimuli

what is the CNS

• The CNS is the brain and spinal cord

what is the pathway through the nervous system?

stimulus → receptor → coordinator → effector → response

what is a reflex response?

• An involuntary (or reflex) response does not involve the conscious part of the brain as the coordinator of the reaction

what should reflex responses be ?

automatic and rapid – this helps to minimise damage to the body

Sensory neurones?

• carry impulses from sense organs to the CNS (brain or spinal cord)

relay neurones

• found inside the CNS and connect sensory and motor neurones

• Motor neurones

• Motor neurones carry impulses from the CNS to effectors (muscles or glands)

what are neurones separated by ?

• they are separated by junctions (gaps) called synapses

RP7: Reaction Time

control variables : The person catching the ruler using their dominant hand each time

independent variable: distracts, backround sound , tiredness

dependant variable: reaction time

• One person sits on a chair with the arm resting on the table

• Person one catches the ruler as quickly as possible record the number on the ruler that is level with the thumb repeat several times

  After person who has completed the test change one factor drink a caffeinated drink or play loud music record all results

• Use a conversion table to convert root measurements into reaction time

• Calculate the mean and eliminate any anomalies

The cerebral cortex

• this is the outer layer of the brain

• It’s highly folded

• responsible for higher-order processes such as intelligence, memory, consciousness and personality

The cerebellum

this is underneath the cerebral cortex and is responsible for balance, muscle coordination and movement

medulla

• this region controls unconscious activities such as heart rate and breathing

why is the brain difficult to study?

• The brain is incredibly complex and delicate making it extremely difficult to study.

• Different areas can't be studied in isolation.

• Treating brain damage and diseases is very difficult. Any potential treatment carries risk of further damage.

• Accidental damage could lead to speech or motor issues or changes to personality, which are permanent.

How do scientists map the regions of the brain?

They electrically stimulate different parts to measure activity

use MRI scanning

Function of the eye?

• The eye is a sense organ containing receptor cells which are sensitive to light intensity and colour

• The purpose of the eye is to receive light and focus it onto the retina at the back of the eye

two main functions of the eye

• adaptation to bright or dim light

• accommodation to focus on near or distant objects

retina

Controls the light receptor cells that detect light intensity and colour of light

optic nerve

Sensory neurone that carries electrical impulses from the eye to the brain

sclera

white layer of the eye that covers the eyeball

cornea

transparent covering of the front of the eye that refracts light

iris

controls how much light enters the pupil

ciliary muscles

Ring of muscles around the lens which relaxes and contracts to change the shape of the lens

suspensory ligaments

Ring of muscles around the lens which relaxes and contracts to change the shape of the lens

lens

Transparent disc that changes shape to focus light onto the retina

what is adaptation?

The process by which the eye adjusts to changes in light conditions, allowing vision in both bright and dim environments.

what happens in dim light?

The pupils dilate to allow more light into the eye.

what happens in bright light?

The pupils constrict to reduce the amount of light entering the eye.

what is accommodation?

The adjustment of the eye's lens to focus on objects at different distances, enhancing clarity and sharpness of vision.

focusing on a near object means that :

• the ciliary muscles contract,

• causing the lens to become thicker for better focus.

• suspensory ligaments loosen

Focusing on a distant object:

• The ciliary muscles relax,

• lens becomes thinner,

• clearer vision of faraway objects,

• suspensory ligaments tighten.

Myopia - short sightedness

• lens is too thick and curved

• image is in front of the retina

• eyeball is too elongated

hyperopia - long sightedness

• image is bought into focus behind the retina

• eyeball is too short

how do we fix myopia?

• concave lens

how do we fix hyperopia?

what are some alternative treatments to eye defects?

• Hard and soft contact lenses:

• Laser surgery:

• Lens replacement surgery