Biology - Response and Regulation

Nervous system

Made up of the brain and spinal cord (CNS), and nerves

How does the nervous system control movement?

By sending electrical signals (nerve impulses) along a network of specialised nerve cells known as neurones.

What are the 3 types of neurons?

• Sensory - Impulses from receptors to the CNS

• Relay - Impulses from sensory to motor neurons

• Motor - Impulses from CNS to effectors (muscles and glands)

What is a synapse?

A small gap between neurones across which a nerve impulse is transmitted through neurotransmitters

What are sense organs?

A group of receptor cells that detect specific stimuli (environmental and internal changes) and send info to the CNS.

An example of a sense organ

The eye responds to light

What is a reflex?

An automatic response to a stimulus by the body.

Reflexes are…

Fast, Automatic, Protective

Types of reflexes:

• Withdrawal - Pulling away

• Pupil - Pupils constrict to prevent damage to the eye from bright light

• Blink - Protects the eyes from foreign bodies

What is a reflex arc?

The nerve pathway involved in a reflex action

What is the Reflex arc pathway?

Stimulus → Receptor → Sensory neurone → Relay neurone → Motor neurone → Effector → Response

Structure of the eye

Function of the Lens

Refracts light, focusing it on the retina

Function of Pupil

Allows light to enter the eye

Function of Iris

Controls the size of the pupil to alter how much light enters the eye

Function of Cornea

Refracts light entering the eye

Function of Retina

Converts light energy into neural signals which are sent to the brain via optic nerve

Function of Choroid

Absorbs light, preventing internal reflection

Function of Sclera

Maintains eyeball shape

Function of Optic nerve

Transmits nerve impulses to the brain from the retina

What’s the blind spot?

When the optic nerve leaves the eye

What is Homeostasis?

Maintaining a stable internal environment

Why is homeostasis important?

To ensure optimum conditions for enzymes and cellular processes in the body. Temperature, blood glucose concentration and water levels must be maintained.

What is a Hormone?

A chemical messenger

What happens if blood glucose concentration rises too high?

The body becomes dehydrated

What happens if blood glucose concentration becomes too low?

The rate of cellular respiration decreases

What hormones control blood glucose concentration?

Insulin and Glucagon which are secreted by the pancreas

What is the effect of Insulin?

• Causes liver and muscle cells to increase their uptake of glucose

• Glucose is converted into glycogen, a storage molecule

What is the effect of Glucagon?

• Causes the breakdown of glycogen to glucose in the liver

• Glucose is released into the blood

What is Negative Feedback?

Any change from the balance in internal conditions results in the body’s hormonal and nervous systems compensating for the change and restoring the balance.

What happens when Blood Glucose concentration increases too high?

• Pancreas secretes Insulin and stops producing Glucagon

• Liver converts Glucose to Glycogen which is stored

• Blood glucose decreases and returns to normal level

What happens when Blood Glucose concentration decreases too much?

• Pancreas secretes Glucagon and stops producing insulin

• Liver converts Glycogen into Glucose which is released into the blood

• Blood glucose increases returning to normal level

What is Diabetes?

When the control of blood glucose levels stops working

What is the cause of Type 1 Diabetes and how do you treat it?

• When the Pancreas doesn’t produce enough insulin

• Insulin injections, manage diet, regular testing glucose levels

What is the cause of Type 2 Diabetes and how do you treat it?

• When you become insulin resistant

• Manage diet, Regular exercise

What happens when your body is too hot

• Vasodilation: Blood vessels dilate near the surface of the skin, blood flows closer. More heat is lost.

• Sweating: Heat energy is used to evaporate sweat, body temp decreases

• The erector muscles relax, hair lies flat

What happens when your body is too cold?

• Vasoconstriction: Blood vessels constrict, so less blood flows closer to the skin surface. Less heat is lost.

• Little sweat

• Erector muscles contract, hairs stand and pockets of air are created as a layer of insulation

• Shivering, muscles contract and heat energy is generated

Lifestyle factors

• Obesity - Increases risk of Type 2 diabetes

• Drugs - Affects chemical processes in the body and has damaging side effects

• Alcohol - Decreases reaction time and causes liver damage, cardiovascular disease

What are Plant tropisms?

Growth responses of a plant to stimuli

What is Phototropism

• A plant’s growth response to light

• Positive - Plant shoots grow towards light

• Negative - Roots grow away from the light

What is Gravitropism?

• A plant’s growth response to gravity

• Negative - Plant shoots as they grow away from gravity

• Positive - Plant roots as they grow towards gravity

What is the importance of plant tropisms?

• Increase a plant’s chance of survival

• Enable them to respond to their environment