Lesson 4: The Brain Flashcards
The Brain
The brain coordinates homeostasis within the
body.
The brain processes the information that is transmitted through the senses so the body can deal with changes in the external and internal environment.
The human brain makes up only 2% of the body weight but at any one time it contains 15% of the body’s blood supply and consumes 20% of the blood’s oxygen and glucose.
Research based on scanning technologies such as PET scans and MRI’s has produced
information about the functions of each part of
the brain.
The Brainstem
The area of the brain that connects the brain to the spinal cord.
Integrates all incoming information
Made up of three parts:
Midbrain
Pons
Medulla Oblongata
Midbrain
Smallest part of the
brainstem
Coordinates vision and
hearing impulses.
Pons
Links the cerebellum to the
cerebral cortex.
Medulla Oblongata
The medulla oblongata is attached to the spinal cord at the base of the brain.
The medulla oblongata has many important functions:
- The cardiac centre controls heart rate and the force of the hearts contractions
- The vasomotor centre adjusts blood pressure by controlling the diameter of
blood vessels - The respiratory centre controls the rate and depth of
breathing. - Also contains reflex centres
for vomiting, coughing, hiccupping and swallowing.
Damage to this part of the brain is usually fatal.
Cerebellum
Contains 50% of the brain’s neurons and controls Muscle co-ordination.
If you stand in one place, specific muscles are contracted while others are relaxed. As groups of muscle fibres become fatigued , others are contracted to
compensate. It does not make decisions about which muscles will contract, it
coordinates the timing of contractions.
The position of the head, limbs and other parts of the body all affect decisions as to
which muscles should be involved. This series of decisions is complex and
develops over time.
Thalamus
Part of a section of the brain
known as the diencephalon.
The thalamus receives
sensations of touch, pain, heat and cold as well as information from the muscles and sends them to the appropriate centers
of the brain.
Hypothalamus
Also part of the diencephalon.
The hypothalamus is the main control centre of the autonomic nervous system.
Enables the body to respond to external threats by sending impulses to various internal organs via the sympathetic nervous system.
Re-establishes homeostasis after the threat has passed, by stimulating the
parasympathetic nervous system.
Cerebrum
The part of the brain where all information from
the senses is sorted and interpreted.
Voluntary muscles that control speech and
movement are stimulated from the cerebrum.
Memories are stored and decisions are made in
the cerebrum.The cerebrum is divided into two halves –
the left and right hemispheres. The two
hemispheres are joined by the corpus callosum.
The corpus callosum is a layer of white matter that is made up of axons which transfer information between the hemispheres.
The cerebral cortex covers each hemisphere of the brain. This is made up of grey matter, which is composed of cell bodies and dendrites packed closely together for maximum interaction.The cerebrum is further divided into 4 lobes:
Frontal lobe – involved in control of muscles and reasoning – allows us to
think critically and plan our actions.
Parietal lobe – receives information from the skin and skeletal muscles and is
associated with our sense of taste.
Occipital lobe – receives information from our eyes.
Temporal lobe – receives information from our ears.
Homunculus
Homunculus means “miniature man”
These were created as representations of the human body as perceived by the
brain.
This is based on work done to determine where sensory and motor nerves end in the parietal lobe of the brain.
The larger the area of the body is on the homunculus; the more nerves there are
that connect to that part of the brain.
