control and coordination 3 Flashcards
describe in brief the role of brain
The brain is the central information processing organ of our body, and
acts as the ‘command and control system’. It controls the voluntary
movements, balance of the body, functioning of vital involuntary organs
(e.g., lungs, heart, kidneys, etc.), thermoregulation, hunger and thirst,
circadian (24-hour) rhythms of our body, activities of several endocrine
glands and human behaviour. It is also the site for processing of vision,
hearing, speech, memory, intelligence, emotions and thoughts
how i the brain protected
The human brain is well protected by the skull. Inside the skull, the
brain is covered by cranial meninges consisting of an outer layer called
dura mater, a very thin middle layer called arachnoid and an inner layer
(which is in contact with the brain tissue) called pia mater.
what are the major parts of the forebrain
The forebrain consists of cerebrum, thalamus and hypothalamus
(Figure 21.4). Cerebrum forms the major part of the human brain. A deep
cleft divides the cerebrum longitudinally into two halves, which are termed
as the left and right cerebral hemispheres. The hemispheres are
connected by a tract of nerve fibres called corpus callosum. The layer of
cells which covers the cerebral hemisphere is called cerebral cortex and is
thrown into prominent folds.
where is grey matter and white matter present in the brain
The cerebral cortex is referred to as the grey
matter due to its greyish appearance. The neuron cell bodies are
concentrated here giving the colour.
Fibres of the tracts are covered with the myelin sheath,
which constitute the inner part of cerebral hemisphere. They give an
opaque white appearance to the layer and, hence, is called the white matter.
what are association areas of the cerebrum
The cerebral cortex contains motor
areas, sensory areas and large regions that are neither clearly sensory
nor motor in function. These regions called as the association areas are
responsible for complex functions like intersensory associations, memory
and communication.
describe thalamus and hypothalamus
The cerebrum wraps around a structure called thalamus, which is a major
coordinating centre for sensory and motor signaling. Another very
important part of the brain called hypothalamus lies at the base of the
thalamus. The hypothalamus contains a number of centres which control
body temperature, urge for eating and drinking. It also contains several
groups of neurosecretory cells, which secrete hormones called
hypothalamic hormones.
what is limbic systme?
The inner parts of cerebral hemispheres and a
group of associated deep structures like amygdala, hippocampus, etc.,
form a complex structure called the limbic lobe or limbic system. Along
with the hypothalamus, it is involved in the regulation of sexual behaviour,
expression of emotional reactions (e.g., excitement, pleasure, rage and
fear), and motivation.
what is mid brain
The midbrain is located between the thalamus/hypothalamus of the
forebrain and pons of the hindbrain. A canal called the cerebral aqueduct
passess through the midbrain. The dorsal portion of the midbrain consists
mainly of four round swellings (lobes) called corpora quadrigemina.
what is the hind brain
The hindbrain comprises pons, cerebellum and medulla (also called
the medulla oblongata). Pons consists of fibre tracts that interconnect
different regions of the brain. Cerebellum has very convoluted surface in
order to provide the additional space for many more neurons. The medulla
of the brain is connected to the spinal cord. The medulla contains centres
which control respiration, cardiovascular reflexes and gastric secretions.
what is brain stem
Three major regions make up the brain stem; mid brain, pons
and medulla oblongata. Brain stem forms the connections between
the brain and spinal cord.
define reflex action
The entire process of response to a
peripheral nervous stimulation, that occurs involuntarily, i.e., without
conscious effort or thought and requires the involvment of a part of the
central nervous system is called a reflex action.
describe the reflex arc
The reflex pathway
comprises at least one afferent neuron (receptor) and one efferent (effector
or excitor) neuron appropriately arranged in a series (Figure 21.5). The
afferent neuron receives signal from a sensory organ and transmits the
impulse via a dorsal nerve root into the CNS (at the level of spinal cord).
The efferent nueuron then carries signals from CNS to the effector. The
stimulus and response thus forms a reflex arc as shown below in the
knee jerk reflex.
