Unit 2.5 Nervous system, Homeostasis, The Eye and The Plant Response

What is the central nervous system (CNS)

The Brain and Spinal cord

What are the sense organ?

It is a group of receptor cells that detect specific stimuli (change in environment and internal). It then sends the information to the central nervous system along neurones

Give an example of stimulus

Chemical, temperatures, light and sound

What is a nerve

A group of neurones that transfer information as electrical impulses in the nervous system

What is a nerve

A group of neurones that transfer information as electrical impulses in the nervous system

What is the nervous system made up of

The brain, spinal cord and nerves

What is the function of the nervous system

Allows an organism to rapidly react to the environmental and internal change

What is the function of sensory neurone

Carries the impulse from sense organs (receptors’) to the central nervous system

What is the function of motor neurones

Carry impulses from the central nervous system to effectors

Describe reflex

• Very rapid

• Automatic

• Protective mechanisms

• The brain is not involved

Give some example of reflexes

• Pull hand away from pain

• Blink

• Pupil constrict in bright light

What does the reflex arc involves

• Stimulus

• Receptors

• Coordinator

• Effector

• Response

What is the role of coordinator

Coordinate information from the receptor and transmits impulses to the effector

Describe the reflex arc

Stimulus —> Receptor —> Sensory Neurones —> Relay Neurones —> Motor neurone —> Effector —> Response

Outline the function of relay neurone

Carries impulses from sensory neurones to motor neurones within the central nervous system

What is a synapse

A small gap between neurones across which a nerve impulses is transmitted via neurotransmitter

Why is reflex automatic?

Impulse does not travel through the neurones in the Brian

Why is reflex fast?

Impulse must only cross through two synapses (which slows them down) in the spinal cord

Label the eye

A = Pupil

B = Iris

C = Lens

D = Cornea

E = Retina

F = Choroid

G = Sclera

H = Optic nerves

I = Blind spot

Outline the structure and function of the cornea

It is a transparent outer covering of the eye and it refracts the light entering the eye

Outline the function of iris

It controls the size of the pupil to layer how much light enters the eye

What is the pupil

A hole that allows light to enter the eye

Outline the function of the lens

it is a transparent disc that can change shape to focus light into the retina

Outline the function of choroid

It absorbs light, preventing internal reflection

Outline the function of the sclera

Maintain eyeball shape

Outline the function of the retina

It converts light energy into neural signal which are sent to the brain via the optic nerve

What is the function of the optic nerve

It transmits nerve impulses to the brain from the retina

What is the blind spot

It is where the optic nerve connects, no receptor cells here.

What are plant tropisms

The growth response of a plant to a stimulus

What is a positive tropisms

The growth of a plant towards a stimulus

What is a negative tropism

The growth of a plant away from a stimulus

What are the 2 main type of plant tropism

1. Geotropic - a plant’s growth response to gravity (grow in the direction of gravity (down))

2. Phototropic - a plant’s growth responses to light (grow in the direction of light)

What are auxins

Auxin is the plant hormones, it is the hormones that control the plant growth in root and shoot.

Where are auxin produced

Meristem

What direction do the root and shoot of a plant grow in

Root = geotropic

Shoot = phototropic

Why is homeostasis important

It ensures the optimum conditions for enzymes and cellular processes in body is reached

What type of chemical helps to ensure optimum condition are reached within the human body

Hormones

What is a hormones

A cell signalling molecule produced by endocrine glands and released into the blood, it travels to a target organ and binds, imitating a response

State the three condition within the human body that must be controlled by homeostasis

• Temperature

• Blood glucose concentration

• Water level

Why must body temperature be controlled

Because enzymes works best at their optimum temperature (37 degree)

Label

Outline the response of the human body to an increase in temperature above 37 degree [3]

• Vasodilation

• Sweating

• Erector muscle relax, hair lies flat

What structure in human body produce sweat

Sweat glands

How does sweating help to reduce body temperature

Heat energy is used to evaporate sweat. Increased heat transfer from the skin to the environment decreases the body temperature

What is vasodilation

Dilation of blood vessels near the skin surface, blood flows closer to the skin surface and greater heat loss to the surrounding

Outline the response of the body to a decrease in temperature below 37 degree [4]

• Vasoconstriction

• Shivering

• Hair erector muscle contract

• Little to no sweat is produced

How does shivering help to increase body temperature

Involuntary contraction of muscles generates heat energy from respiration

How does the contraction of hair erector muscles help to increase body temperature

Hairs stand on the end creating pockets of air between hairs and a layer of insulation

What is vasoconstriction

Constriction of blood vessels near skin surface, less blood flows close to the skin surface and less heat is loss to the surroundings

Why must blood glucose concentration must be controlled

• If blood glucose concentration is too high, it can cause dehydration and type 2 diabetes

• If blood glucose concentration is too low, the rate of cellular respiration can decrease

Which organ is responsible for the maintenance of blood glucose concentration

Pancreas

Describe what would happen if someone did not eat for a while and what would happen if someone suddenly takes a sugary drink

It you did not eat for a while, chemoreceptor will detect the blood sugar level is low, so the pancreas will produce glucagon ta breaks the glycogen in your liver to convert it into glucose so the blood sugar is maintain at the certain range

If you rook a sugary drink, then the chemoreceptor will detect the blood sugar level too high, so the pancreas will produce insulin to convert glucose in the liver into glycogen to reduce the blood sugar level.

Why does someone’s glucose level increase when eat glucose

The glucose taken are absorbed into the blood stream

What is the control of blood glucose concentration an example of

Negative feedback

What is diabetes

A condition where the homeostatic control of blood glucose levels stops working.

What is the cause of type 1 diabetes

Immune system attacks and destroys insulin producing cells, therefore pancreas does not produce enough insulin

How can type 1 insulin be treated [3]

• Daily insulin injection

• Managing diet

• Regularly testing blood glucose level

What is the cause of type 2 diabetes

Person develops insulin resistance (often due to obesity)

How can type 2 diabetes be treated [3]

• Managing diet

• Regular exercise

• Drugs

Describe the effect of alcohol on the body

• Decrease reaction time

• Cause liver damage and cardiovascular diseases

Name the receptor that reacts to the flashing of intense light

Retina