LIFE SCIENCES - HUMAN RESPONSE TO THE ENVIRONMENT

Receptor

A structure that receives a stimulus and converts it into an impulse

Effector

Gland or organ that brings about a response to stimuli received by the body

Stimulus

Detectable change in the internal or external environment

Impulse

Electrical signal created by receptor organs in response to stimuli

Autonomic nervous system

Controls our involuntary bodily functions; divided into the parasympathetic and sympathetic nervous system

Peripheral nervous system

consists of nerves that extend outside the central nervous system (brain and spinal cord)

Co-ordinating system

consist of receptors and effectors which respond to stimuli and allow for changes to take place to maintain internal conditions

nervous system

endocrine system

Cranium

part of the skull that contains and protects the brain

Meninges

protective membranes surrounding the brain and spinal cord

Cerebrospinal fluid

fluid around the brain and spinal cord to aid in protection

Grey matter

part of the brain and spinal cord consisting of cell bodies and dendrites

White matter

part of the brain and spinal cord consisting of myelinated axons

Neuron

specialized nerve cells which transmits nerve impulses

Dendrites

fibers that transmit impulses to a cell body in a neuron

Nerve

bundle of neurons

Synapse

the gap between the axon of one neuron and dendrite of another

Neurotransmitter

chemicals which transfer impulses across the synapse

Homeostasis

the tendency of living organisms to maintain their internal environment constant within narrow limits irrespective of changes in the external environments

Alzheimer's disease

disease caused by nerve defects, usually in older people (over 60 as young as 40) and is characterized by memory loss and confusion

Multiple sclerosis

disease caused by the body's immune system attacking the myelin sheath covering neurons which prevents them from functioning properly and is characterized by loss of speech and vision, difficulty walking, pain, fatigue and memory loss (ages 20 and 40)

Division of human nervous system

central nervous system (brain and spinal cord)

peripheral nervous system (autonomic and somatic)

Internal changes

body temperature

sugar levels

CO2 and O2 levels

water levels

External changes

pain

environment temperature

danger

The brain

Made up of delicate nervous tissue which cannot repair itself.

Controls all functioning of human body.

Protection of the brain

Inside bony cranium

Surrounded by three membranes (meninges)

Cushioned by fluid (cerebrospinal fluid)

Structure of the brain

Cerebrum structure

largest part of the brain

divided into 2 hemispheres which are connected by corpus callosum

Cerebrum function

controls voluntary actions

receives and interprets sensations from sense organs

higher though processes(memory, intelligence, reasoning)

allow communication between 2 halves of brain

Cerebellum structure

second largest

located inside and below cerebrum

Cerebellum function

co-ordinates skeletal muscles to bring about balance while moving

maintains balance and posture

maintains muscle tone

Medulla oblongata structure

lower part of brain

continues down into body as the spinal cord

Medulla oblongata function

controls breathing, peristalsis, heartbeat, swallowing

transmits impulses from spinal cord to brain

controls less important reflexes: blinking, coughing, sneezing, salivating

Hypothalamus structure

small section of brain just above pituitary gland

Hypothalamus function

control centre for things such as hunger, thirst, sleep, body temperature and emotions

The internal structure of the spinal cord

The spinal cord

Made up of delicate nerve tissue which cannot repair itself

Spinal cord protected by

33 vertebrae (bone) with discs of cartilage between them to act as shock absorbers

three membranes (meninges)

cerebrospinal fluid

Spinal nerves

31 pairs of nerves arising from the spinal cord

Dorsal root (enters)

Ventral root (leaves)

Spinal cord functions

transmits impulses from receptors to the brain and from the brain to effectors

contains reflex centres that function automatically to protect the body

4 structures of neurons

*dendrites - transmitting impulses towards the cell body

*cell body (with nucleus) - controlling cell metabolism

*axon - transmitting impulses away from the cell body

*myelin sheath - insulating axon and speeding up transmission of impulses, enclosed by neurilemma (repair)

Structure of a motor neuron

1. dendrites

2. cell body

3. axon

4. myelin sheath

5. terminal end of axon

3 types of neurons

sensory neurons, motor neurons, interneurons

Sensory neurons

transmits impulses from receptors to the central nervous system

Interneuron

connects a sensory neuron to a motor neuron in the central nervous system

Motor neuron

transmits impulses from the central nervous system to the effectors (muscles and glands) in the body

Significance of a synapse

*ensures impulse moves in one direction only

*prevents continuous stimulation of neurons

*ensures impulses are transmitted from the sensory neuron to the motor neuron

Reflex action

quick, automatic response to a stimulus

(knee-jerk, sneezing, quickly removing body part from danger)

Reflex arc

pathway along which an impulse is transmitted to bring about a response to a stimulus during a reflex action

Receptor => sensory neuron => spinal cord =>connector neuron => motor neuron => Effector

Significance of reflex action

allows for quick response, without thinking, to protect the body from damage and danger

Reflex action of a person touching a hot pot:

1. Stimulus detected by receptors and converted into a nerve impulse.

2. The nerve impulse is transmitted along the sensory neuron through the dorsal root to the spinal cord.

3. The impulse is transmitted from the sensory neuron to an interneuron in the spinal cord.

4. The impulse is transmitted from the interneuron to a motor neuron in the spinal cord.

5. The impulse exits the spinal cord through the ventral root and is transmitted along the axon to the effector organs (muscle in arm contracts).

6. The hand pulls away from the stimulus quickly.

Does reflex action include the brain?

No, impulses reach the brain after the reflex arc is complete and pain will be felt.

Peripheral Nervous System can be divided:

Somatic - voluntary muscles

Automatic - involuntary muscles

Peripheral Nervous System functions:

transmits impulses from receptors to central nervous system via sensory neurons

transmits impulses from the central nervous system to effectors via the motor neuron

Somatic Nervous System (SNS)

External environment

Automatic Nervous System (ANS)

Internal environment (homeostasis)

*sympathetic nervous system

*parasympathetic nervous system

Sympathetic nervous system

responsible for fight or flight function in emergency situations

Parasympathetic nervous system

restores body to a normal state after an emergency situation

Effects of sympathetic and parasympathetic nervous systems

sympathetic:

*increases heart rate

*increases blood pressure

*constricts blood vessels in the skin (vasoconstriction)

*widens bronchioles

*decreases peristalsis

*stimulates sweat secretion

*stimulates secretion of adrenaline

*dilates pupils

parasympathetic:

*decreases heart rate

*decreases blood pressure

*dilates blood vessels in skin (vasodilation)

*narrows bronchioles

*increases peristalsis

*no effect on sweat secretion

*no effect on adrenaline secretion

*constricts pupil

Brain injuries

Affect movement, memory and speech

long-term mental health issues

Spinal cord injuries

paralysis and the inability to move or feel below the point of injury

grommets

tiny hollow plastic button used to drain fluid from the ear via the tympanic membrane

functions of the ear

hearing and balance

Organ of Corti

converts stimulus of sound to impulse

function of eustachian tube

equalize pressure on either side of the ear drum

function of the auditory nerve

carries impulses from the cochlea to the brain

function of tympanic membrane

transmits sound from the air to the ossicles inside the middle ear and then to the cochlea via vibrations

function of ossicles

to transmit and amplify vibrations from the eardrum to the inner ear

function of pinna

traps sound waves and directs them to the auditory canal

function of auditory canal

carries sound waves to the ear drum

prevents drying out of the ear by secreting wax

myopia

nearsightedness - needs concave lens

pupillary reflex

The automatic process by which the iris contracts and relaxes to control the size of the pupil, in response to the relative brightness of light entering the eye

accomodation of lens

lenses change shape to focus on objects near or far

Hypermetropia

farsightedness - needs convex lenses

astigmatism

a condition in which the eye does not focus properly because of uneven curvatures of the cornea

Cataracts

clouding of the lens

conjuctiva

the mucous membrane that covers the front of the eye and lines the inside of the eyelids.