HUMAN RESPONSES TO THE ENVIRONMENT Two systems to be studied: 1.Nervous system 2.Endocrine system

Introduction To survive all organisms have to react to changes in their external and internal environment External environment: Environment outside the body for example of factors that might change are temperature, light, etc in their natural environment or habitat. Internal environment: Environment inside the body e.g. concentration of CO 2, O 2, H 2 O around cells/tissues/organs inside the body.

Introduction (cont.) Human response to these changes in the environment occurs to maintain stability/balance within the organism. Organisms sense changes in the environment as a stimulus. These impulses are send to the brain which interpret the information and sends a different message back to the part of the body telling it how to react.

Homeostasis The body works hard to keep its internal environment as constant as possible. All the organs and systems of the body work together to create this stable internal condition. The process of maintaining a constant cell environment in the body is called homeostasis. The endocrine and nervous systems, as our co-ordinating systems, play a very important part in regulating homeostasis. Examples: Blood pressure, glucose levels in the blood, ect.

Human Nervous system What to learn: Structure of 3 types of neurons, nerve bundles transmission of an impulse (Making of drawings) CNS, Peripheral, Autonomic (sympathetic & parasympathetic), disorders Difference between reflex arc and reflex action Structure and functioning of a simple arc, Significance of a reflex arc Sense organs (Ear and Eye)

Co-ordination in Humans Nervous co-ordination Chemical co-ordination Central nervous system Peripheral and autonomic nervous systems Sense receptors and organs Endocrine system Feedback mechanisms Over- & under- secretion

Human nervous system – is a complex system

Cross-section of the human brain showing the different parts

Functions of certain parts of the brain Cerebellum Co-ordinates movements of your voluntary muscles Maintains your balance by controlling muscle tension

Functions of certain parts of the brain Hypothalamus Controls your blood pressure Controls your body temperature Regulates your levels of thirst and hunger Regulates emotions such as anger and pleasure Regulates your sleep patterns

Functions of certain parts of the brain Cerebrum Controls all voluntary muscle actions Receives and interpret sensations of sight, hearing, taste, smell, touch and speech Responsible for higher thought processes such as memory, reasoning, judgement and intelligence Responsible for behaviour and emotions

Functions of certain parts of the brain Medulla oblongata (same structure as the spinal cord) Controls important involuntary actions such as heartbeat and breathing Enables each half of your brain to control the opposite side of your body Transmit nerve impulses between the spinal cord and the brain

CROSS-SECTION OF SPINAL CORD

Functions of the spinal cord Links the brain with all the organs of the body (except those in the head & neck) Carries sensory information to the brain for interpretation Carriers then motor information from the brain to the effectors (muscles and glands) It’s a centre for the reflex action, which enables the body to respond very quickly to harmful stimuli using the reflex arc

A typical nerve cell – A NEURON

Example of a reflex arc