- Organisms need to detect and respond to stimuli to adapt, react to their surroundings and survive in a
continuously changing environment.
• A stimulus is any internal or external environmental change to which an organism responds
Stimulus = singular stimuli = plural
- Examples include light, sound, touch, temperature etc.
o Simple animals such as amoeba respond to stimuli but don't need a system to coordinate their response.
o As animals advance and develop organs and systems the need for coordination arises.
o Different body systems must be linked so that control movement and responses are possible.
→ It's essential that cell activities in different parts of the body or coordinated and integrated
- There are two coordinating systems in complex animals:
o Nervous system
o Endocrine system (hormones)
- These systems work together for communication and homeostasis in the body, by responding to stimuli.
Homeostasis is vital survival of organisms as they only function within a specific range of conditions
(e.g. optimum temperature or oxygen levels)
- When rapid responses are required, impulses are conducted in nerves; it is known as nervous
coordination.
- When slower responses like growth and digestion are required, hormones (chemical messengers) are
transported in the blood; it is known as chemical coordination.
- The nervous system enables humans to respond to stimuli. A stimulus must first be detected, processed
and integrated before response can take place.
Processing
Stimulus Detection and Responce
Intergration
- When the receptors detect a stimulus, it is conducted as a nerve impulse along a network of nerve cells
to the central nervous system (brain and spinal cord) where the information is processed and
integrated.
- The process information is been conducted as nerve impulses from the brain and spinal cord, via nerve
cells to the effectors.
- Effectors are the organs (muscles or glands) that respond to the original stimulus.
,HUMAN NERVOUS SYSTEM
The human nervous system is subdivided into 2 main groups:
- Central nervous system (CNS) consisting of the brain and spinal cord.
- Peripheral nervous system (PNS) consisting of nerves that conduct nerve impulses to and from the brain
and the spinal cord. It includes twelve pairs of cranial nerves and 31 pairs of spinal nerves.
Subdivisions of The Nervous System
CENTRAL NERVOUS SYSTEM
- The main function of the central nervous system is to receive nerve impulses from the receptors, interpret
the information and transmit it to the effectors to bring about the desired response.
Protection of the Central Nervous System
- Nervous tissue is very soft and most cells cannot repair or regenerate themselves. It must be well
protected against injuries.
- The central nervous system is surrounded externally by bone. The brain is enclosed by the skull and the
spinal cord by the vertebral column.
, The 33 vertebrae form the vertebral column (bone tissue) with the vertebral canal in which the spinal cord
(nerve tissue) occurs.
- The cartilaginous disks between the vertebrae and the S-shaped curvature aid shock absorption And
make the vertebral column more flexible.
- Internally the brain is enveloped by three meninges (cerebral membranes):
o The pia mater - the innermost membrane that is tightly wrapped around the brain and spinal cord
and rich in blood vessels; providing oxygen and nutrients to the central nervous system.
o The dura mater - the tough outermost membrane that lines the skull cavity and spinal canal.
o The arachnoid membrane - a thin membrane between the pia mater and the dura mater.
- Between the pia mater and the arachnoid is a space filled with cerebrospinal fluid.
Functions of Cerebrospinal Fluid
- Shock absorber
- Supplies
neurons
(nerve cells)
with nutrients
and oxygen
- Removes
waste
- Prevents
dehydration
of neurons
- Maintains
constant pressure around the CNS
Gray Matter vs White Matter
- Both the brain and the spinal cord consist of grey matter and white matter.
o Grey matter - consists of darker cell bodies and dendrites of neurons.
o White matter - consists of myelinated axons that appear white due to the fatty myelin sheath that
enclose the axons.
- The Gray matter in the brain is mostly on the outside and surrounds the white matter.
- It is the opposite in the spinal cord i.e. the white matter is on the outside and the H-shaped grey matter
on the inside.
continuously changing environment.
• A stimulus is any internal or external environmental change to which an organism responds
Stimulus = singular stimuli = plural
- Examples include light, sound, touch, temperature etc.
o Simple animals such as amoeba respond to stimuli but don't need a system to coordinate their response.
o As animals advance and develop organs and systems the need for coordination arises.
o Different body systems must be linked so that control movement and responses are possible.
→ It's essential that cell activities in different parts of the body or coordinated and integrated
- There are two coordinating systems in complex animals:
o Nervous system
o Endocrine system (hormones)
- These systems work together for communication and homeostasis in the body, by responding to stimuli.
Homeostasis is vital survival of organisms as they only function within a specific range of conditions
(e.g. optimum temperature or oxygen levels)
- When rapid responses are required, impulses are conducted in nerves; it is known as nervous
coordination.
- When slower responses like growth and digestion are required, hormones (chemical messengers) are
transported in the blood; it is known as chemical coordination.
- The nervous system enables humans to respond to stimuli. A stimulus must first be detected, processed
and integrated before response can take place.
Processing
Stimulus Detection and Responce
Intergration
- When the receptors detect a stimulus, it is conducted as a nerve impulse along a network of nerve cells
to the central nervous system (brain and spinal cord) where the information is processed and
integrated.
- The process information is been conducted as nerve impulses from the brain and spinal cord, via nerve
cells to the effectors.
- Effectors are the organs (muscles or glands) that respond to the original stimulus.
,HUMAN NERVOUS SYSTEM
The human nervous system is subdivided into 2 main groups:
- Central nervous system (CNS) consisting of the brain and spinal cord.
- Peripheral nervous system (PNS) consisting of nerves that conduct nerve impulses to and from the brain
and the spinal cord. It includes twelve pairs of cranial nerves and 31 pairs of spinal nerves.
Subdivisions of The Nervous System
CENTRAL NERVOUS SYSTEM
- The main function of the central nervous system is to receive nerve impulses from the receptors, interpret
the information and transmit it to the effectors to bring about the desired response.
Protection of the Central Nervous System
- Nervous tissue is very soft and most cells cannot repair or regenerate themselves. It must be well
protected against injuries.
- The central nervous system is surrounded externally by bone. The brain is enclosed by the skull and the
spinal cord by the vertebral column.
, The 33 vertebrae form the vertebral column (bone tissue) with the vertebral canal in which the spinal cord
(nerve tissue) occurs.
- The cartilaginous disks between the vertebrae and the S-shaped curvature aid shock absorption And
make the vertebral column more flexible.
- Internally the brain is enveloped by three meninges (cerebral membranes):
o The pia mater - the innermost membrane that is tightly wrapped around the brain and spinal cord
and rich in blood vessels; providing oxygen and nutrients to the central nervous system.
o The dura mater - the tough outermost membrane that lines the skull cavity and spinal canal.
o The arachnoid membrane - a thin membrane between the pia mater and the dura mater.
- Between the pia mater and the arachnoid is a space filled with cerebrospinal fluid.
Functions of Cerebrospinal Fluid
- Shock absorber
- Supplies
neurons
(nerve cells)
with nutrients
and oxygen
- Removes
waste
- Prevents
dehydration
of neurons
- Maintains
constant pressure around the CNS
Gray Matter vs White Matter
- Both the brain and the spinal cord consist of grey matter and white matter.
o Grey matter - consists of darker cell bodies and dendrites of neurons.
o White matter - consists of myelinated axons that appear white due to the fatty myelin sheath that
enclose the axons.
- The Gray matter in the brain is mostly on the outside and surrounds the white matter.
- It is the opposite in the spinal cord i.e. the white matter is on the outside and the H-shaped grey matter
on the inside.
