The central nervous system coordinates responses to stimuli through a network of neurons and organs. Homeostasis maintains optimal internal conditions through receptors, coordination centers, and effectors. The nervous system includes specialized cells called neurons that transmit electrical impulses. Reflexes provide rapid, automatic responses to reduce injury risk. The brain processes sensory information and controls both conscious and unconscious activities. Various methods like EEG and MRI scans help study brain function. The eye has several structures adapted for focusing light onto the retina to enable vision.
Structure and Function of the Human Nervous System
The human nervous system regulates internal conditions and responds to environmental stimuli through homeostasis. Key components include:
- Receptors that detect changes in internal or external conditions
- Coordination centers like the brain and spinal cord that process information
- Effectors such as muscles and glands that produce responses
The nervous system consists of specialized cells called neurons adapted for transmitting electrical impulses:
- Sensory neurons carry signals from receptors to the central nervous system
- Motor neurons transmit signals from the CNS to effectors
- Relay neurons in the spinal cord connect sensory and motor neurons
Definition: The central nervous system (CNS) is the main coordination center that receives sensory information and coordinates responses.
Synapses connect neurons and allow signals to be passed through chemical neurotransmitters. The basic pathway is:
Stimulus → Receptor → Coordinator → Effector → Response
Highlight: Neurons have key adaptations like long axons insulated by myelin sheaths to rapidly transmit signals over long distances.
Reflex arcs provide rapid, automatic responses to reduce injury risk without conscious thought. The steps in a reflex arc are:
- Receptors detect a stimulus
- Sensory neurons send signals to relay neurons in the spinal cord
- Motor neurons transmit signals to an effector
- The effector (e.g. muscle) produces a response
Example: Quickly pulling your hand away from a hot surface is an example of a reflex action.
Register
Sign up to get unlimited access to thousands of study materials. It's free!
Access to all documents
Join milions of students
Improve your grades
By signing up you accept Terms of Service and Privacy Policy
The Brain and Methods of Study
The brain is the central processor of the nervous system, receiving sensory input and coordinating responses. Key regions include:
- Cerebral cortex: Controls higher functions like consciousness, intelligence, memory, and language
- Cerebellum: Responsible for muscle coordination
- Medulla: Regulates unconscious activities like breathing and heart rate
Vocabulary: The cerebral cortex is the outer wrinkled layer of the brain responsible for higher cognitive functions.
Scientists use various methods to study brain structure and function:
-
Observing people with brain damage
- Advantages: Non-invasive
- Disadvantages: Cannot identify specific brain regions
-
Electrical stimulation (EEG)
- Advantages: No electricity used, can detect conditions like epilepsy, direct patient feedback
- Disadvantages: Cannot detect cancer, requires expert interpretation, risk of brain damage
-
MRI scans
- Advantages: Quick, accurate diagnosis for many conditions
- Disadvantages: Uses ionizing radiation, risk of allergic reaction to contrast dye
Highlight: Each brain study method has unique advantages and limitations, so researchers often use multiple approaches.
Register
Sign up to get unlimited access to thousands of study materials. It's free!
Access to all documents
Join milions of students
Improve your grades
By signing up you accept Terms of Service and Privacy Policy
The Eye and Vision
The eye is a complex sensory organ adapted for focusing light to enable vision. Key structures include:
- Cornea: Refracts incoming light
- Pupil: The opening through which light enters
- Iris: Controls how much light enters by adjusting pupil size
- Lens: Further refracts and focuses light onto the retina
- Retina: Contains light-sensitive receptors
- Optic nerve: Carries visual signals to the brain
Vocabulary: The sclera is the tough white outer layer that protects the eye.
The eye adapts to changing light conditions:
- In bright light: Circular muscles contract, radial muscles relax, pupil constricts
- In dim light: Circular muscles relax, radial muscles contract, pupil dilates
The shape of the lens can also be adjusted to focus on objects at different distances.
Example: When you move from a dark room into bright sunlight, your pupils quickly constrict to reduce the amount of light entering your eyes.
Register
Sign up to get unlimited access to thousands of study materials. It's free!
Access to all documents
Join milions of students
Improve your grades
By signing up you accept Terms of Service and Privacy Policy
Similar content
Biology - 1.5.2 the human nervous system
notes on the human nervous system
19
376
1
Biology - The Eye
Contains diagrams and descriptions of the anatomy of the eye, along with the iris reflex, accommodation, longsightedness and shortsightedness.
10
202
0
Biology - Control and communication notes
Nat5 biology notes
8
64
0
Biology - b10 The nervous system
this covers all of b10 : homeostasis, negative feedback, the nervous system, reflexes and the required practicle of investigating reactions. This is suitable for anyone who studies GCSE combined science (foundation and higher).
35
883
0
Biology - homeostasis nervous system - AQA BIOLOGY
for combined and triple paper 2 - grade 9 notes
4
231
0
Biology - nervous system flashcarda
.
2
53
0
10