The Human Nervous System Flashcards
The nervous system
The nervous system protects organisms from harm by responding to changes in the environment. It does this by coordinating communication between different parts of organisms.
The brain
The brain is one of the components (parts) of the central nervous system (CNS).
The CNS coordinates the response of effectors. Effectors are muscles or glands that act in response to a change in the internal or external environment.
The spinal cord
The spinal cord is the other component (part) of the CNS. It is also important in coordinating the response of effectors to changes in the environment.
The neurones (nerve cells)
Neurones (nerve cells) carry electrical impulses (signals) between receptors, the central nervous system (CNS) and effectors.
Synapses
At each junction of the reflex arc, there is a synapse. Synapses are gaps between neurones. Nerve impulses must travel across these gaps: The electrical impulse reaches the end of the neurone before the synapse.
This triggers the release of chemicals called neurotransmitters. The neurotransmitters diffuse (move down a concentration gradient) across the synapse. The neurotransmitters bind to receptors on the next neurone.
The presence of the neurotransmitter causes the production of an electrical impulse in the next neurone.
At each junction of the reflex arc, there is a synapse
Synapses allow information to be passed from one neurone to another.
Neurone Structure
Axons carry electrical impulses away from the cell body. Dendrites carry electrical impulses towards the cell body. Axons are covered in a layer called a myelin sheath. This insulates the neurone, so electrical impulses travel down it more quickly.
Axons are covered in a layer
called a myelin sheath. This insulates the neurone, so electrical impulses travel down it more quickly.
Axons are covered in a layer called a myelin sheath
This insulates the neurone, so electrical impulses travel down it more quickly.
Reflex Actions
Reflex actions allow us to respond to dangerous situations rapidly and automatically. Reflex actions do not involve conscious thought. The nervous system responds to stimuli (events or things) via a reflex arc.
Some examples of reflexes are:
Dropping hot objects, Sneezing, Blinking
Reflex actions allow us to
respond to dangerous situations rapidly and automatically. For reflex actions, the nervous system responds to stimuli (events or things) via a reflex arc.
Components of a Reflex Arc
The different parts of a reflex arc are: Stimulus
A stimulus can be any change in the environment to which the body needs to respond.
The stimulus is detected by a receptor.
Components of a Reflex Arc
The different parts of a reflex arc are: Receptor
Receptors are found all over the body.
They detect the change in the environment and initiate (start) a signalling process within the body.
The signal is picked up by a neurone (nerve cell).
Components of a Reflex Arc
The different parts of a reflex arc are: Neurones
There are three types of neurone (nerve cell):
The sensory neurone, which carries the signal in the form of an electrical impulse to the central nervous system (CNS). The relay neurone (in the CNS) relays the electrical impulse from the sensory neurone to the appropriate motor neurone. The motor neurone is another type of nerve cell that carries the electrical impulse from the CNS to an effector.
Components of a Reflex Arc
The different parts of a reflex arc are: effector
An effector is a muscle or gland that brings about an action in response to the change in the internal or external environment.
Components of a Reflex Arc
The different parts of a reflex arc are: response
Response
The response can be any action that helps the organism to avoid the harmful situation.
Reflex Arc
The stimulus is detected by a receptor. The sensory neurone carries the signal, in the form of an electrical impulse, to the central nervous system (CNS). The motor neurone carries the electrical impulse from the CNS to an effector. An effector (a muscle or gland) brings about an action in response to the change in the internal or external environment.
The Brain
The brain is a very complex organ that controls all conscious and unconscious thoughts in order to keep an organism alive.
Brain function
Brain function
The brain is made up of millions of interconnecting neurones (nerve cells).
Different regions of the brain are responsible for coordinating (organising) different functions.
Brain damage
The brain is delicate and complicated.
Therefore, the treatment of brain damage and brain disease is difficult.
Parts of the Brain
The brain is made up of three main parts.
Medulla oblongata
This part is responsible for unconscious activities (e.g. breathing and heartbeat).
Cerebellum
This part is responsible for the muscle coordination.
The cerebellum is important for movement, posture, balance and speech.
Cerebral hemispheres
This part is responsible for conscious thought (e.g. memory, language and intelligence).
In the brain, the cerebellum is
responsible for muscle coordination. The cerebral hemispheres are responsible for conscious thought. The medulla oblongata is responsible for unconscious activities.
Researching the Brain
Many areas of the brain cannot be accessed safely through surgery while people are alive. But neuroscientists (scientists who study the brain) have other ways to understand how the brain works.
PET scans
These scans are used to look at how parts of the brain are functioning.
Using radioactive glucose, the amount of glucose different parts of the brain are using up can be detected.
An image of brain activity is then made
Studying brain damage
By studying patients with brain damage, where part of their brain doesn’t function, neuroscientists have been able to link particular regions of the brain to particular functions.
CT scanning
Lots of x-rays are taken of the brain, and a computer then builds a 3D image of the brain’s structure.
Different types of cells absorb different amounts of the x-rays.
Brain tumours show up as white blotches.
Researching the Brain
Neuroscientists (scientists who study the brain) have been working for many years to further understand how the brain works, using both CT and PET scanning and by studying the effects of brain damage.
Brain Damage
Treating injuries or diseases in the brain or in other parts of the nervous system is very difficult.
Spinal injuries
If the spinal cord is severed (cut), electrical impulses can no longer travel to the brain.
Wires can partly re-connect the spinal cord, but this isn’t very effective.
Neurone damage
Neurones cannot be replaced like other cells in the body, so damage to these cells is often permanent and irreversible. Researchers are trying to find a way to make new neurones using stem cells.
Brain tumours
Brain tumours are lumps of dividing cancer cells. They can block blood flow to other parts of the brain.
These cancers can be treated with chemotherapy (using drugs), radiotherapy (using radiation) or brain surgery, but these also cause lots of damage to the body.
