The Nervous System Flashcards
(16 cards)
Describe the cell types which compromise the different regions of the nervous system
Cell and tissues of the nervous system
- Neurones : nerve cells that generate and transmit electrical impulses called action potential
- Neuroglia : connective tissue that support neurones
- Nerves : made up of various neurones collected into bundles (tracts)
Describe the two parts of the nervous system
1) Central nervous system (CNS) that consists of the brain and spinal cord
2)Peripheral Nervous system(PNS) consists of all the nerves outside the brain and spinal cord including spinal nerves and cranial nerves
The PNS is subdivided into Somatic nervous system and autonomic nervous system. The autonomic nervous system (ANS) is then divided into sympathetic and parasympathetic
Expand on the Somatic nervous system
The somatic nervous system communicates with sense organs and voluntary muscles. It’s divided into sensory(afferent) nervous system : sensory input and motor (efferent) nervous system : motor output
Structure of a neuron
Each neurone has a cell body ,nucleus,dendrites,axon and terminal axon. Neurone cannot divide so for survival they need a supply of oxygen and glucose. Neurones can synthesise chemical energy (ATP) from glucose
Cell body vary in size and shape and form the grey matter of the nervous system
Dendrites are same structure as axon but shorter and branching to receive action potential.
Axons carry the impulse away from the cell body. Some axons are surrounded by a myelin sheath that consists of a series of Schwann cells. There are also myelin-sheath gaps called node of Ranvier that permit saltatory conduction.
Describe the Structure and function of the nervous system
The central nervous system is made up of the brain and the spinal cord. The brain controls most body functions including awareness, movement ,sensation,thought,speech,memory. The human brain is the most complex with a hundred billion neurones with a quadrillion connections between them. It receives 15% of the cardiac output and has a system of autoregulation ensuring blood supply is constant despite potential changes.
The spinal cord is connected to the brain and the brain stem and is covered by vertebrae of the spine. Nerves exit the spinal cord to both sides of the body.
Name the lobes of the brain and examples of the activity it controls
1) Frontal lobe controls problem solving emotional traits and speaking
2) Parietal lobe controls knowing left from right, sensation and reading
3) Temporal lobe controls understanding language, memory and hearing
4) Occipital lobe controls vision and colour perception
5) Brain stem controls breathing, body temperature and swallowing
6) Cerebellum controls balance and fine muscle control
Important structures within the Brain
Cerebral cortex: ultimate control and information processing centre
Corpus callosum: axon fibres connecting two cerebral hemispheres
Thalamus: relays messages between lower brain centres and cerebral cortex
Hypothalamus: controls maintenance functions such as eating; helps govern endocrine system; linked to emotion and reward
Pituitary : master endocrine gland
Reticular formation: helps control arousal
Medulla: controls heartbeat and breathing
Spinal cord: pathway for neural fibres travelling to and from brain; controls simple reflexes
Cerebellum: coordinates voluntary movement and balance
Amygdala: neural centres in the limbic system linked to emotion
Hippocampus: a structure in the limbic system linked to memory
Summarised structure of the brain
Cerebrum: the largest and mostly highly developed part of the human brain. The functions include regulation of muscle contraction, memory storage and processing, production of speech, interpretation of taste and sound
Thalamus acts as a relay station for sensory impulses. It also has a role in memory
Hypothalamus is closely associated with the pituitary gland and produces two hormones: antidiuretic hormone (ADH) and oxytocin. It is the chief autonomic integration centre and is part of the limbic system, which is the emotional brain
Brain stem is associated with the cranial nerves. The structure of the brain stem include the midbrain, pons and the medulla oblongata
Cerebellum coordinates voluntary muscle movement, motor learning, cognitive functions and balance and posture. Although the cerebellum accounts for 10% of the brain’s volume it contains 50% of the total number of neurone in the brain
Describe the vasculature of the brain, it’s ventricles and role of CSF
The Ventricles of the brain are a communicating network of cavities filled with cerebrospinal fluid(CSF). The ventricular system is composed of two lateral ventricles, the third ventricle and the fourth ventricle. The choroid plexuses located in the ventricles produce CSF which fills the ventricles and subarachnoid space following a cycle of constant production and reabsorption
The cerebrospinal fluid (CSF) bathes and cushions the brain and spinal cord within their bony confines. There is approx 150ml of CSF circulating around the brain , in the ventricles and around the spinal cord. The CSF is replaced every 8hrs
Describe the structure of the spinal cord
The adult spinal cord is approx 45cm. There are two layers; an outer layer of white matter and an inner layer made up of grey matter which surrounds a small central canal.
The spinal cord is enclosed within the vertebral canal which forms a protective ring of bone around the cord. Other protective coverings include the spinal meninges which are three layers of connective tissue coverings which extend around the spinal cord.
Functions of the spinal cord
The spinal cord provides a means of communication between the brain and the peripheral nerves that leave the spinal cord and has two major functions in maintaining homeostasis :
The tracts of the white matter of the spinal cord carry sensory impulses to the brain and motor impulses from the brain to the skeletal muscles and other effector muscles
The grey matter in the centre of the cord is shaped like a butterfly and consists of cell bodies of interneurons and motor neurons. The grey matter is a site for integration of reflexes
Somatic nervous system: 1st subdivision of PNS
The somatic nervous system consists of sensory nerves and motor nerves and is associated with the voluntary control of skeletal muscles and sensory organs. This system can receive a sensory input and produce a motor output
2nd Subdivision of PNS : the Autonomic nervous system
The autonomic nervous system (ANS) plays a major role in the maintenance of homeostasis by regulating the body’s automatic, involuntary functions and in common with the rest of the nervous system consists of neurones , neuroglia and other connective tissue
It’s structure is unique and it is divided into two:
The sympathetic division and
The parasympathetic division
Sympathetic nervous system
The sympathetic division includes nerve fibres that arise from the 12 thoracic and first two lumbar segments of the spinal cord, hence it’s also referred as the thoracico-lumbar division
The sympathetic division takes control of many internal organs when a stressful situation occurs
An example of physical stress can be strenuous exercise or emotional stress such as anger or anxiety
Parasympathetic nervous system
The parasympathetic division includes fibres that arise from the lower end of the spinal cord and includes several cranial nerves hence it is referred to as the craniosacral division
The parasympathetic system is most active when the body is at rest and utilises acetylcholine to control all internal responses associated with a state of relaxation. It supports body functions that conserve and restore body energy during times of rest and recovery
Blood supply ,cerebral circulation and spinal circulation
The nervous system is home to the major control system in the body, it’s nourishment and protection are vital for survival. Cells of the nervous system must receive adequate nutrient (glucose) and oxygen : this occurs through the cerebral and spinal circulation.
Cerebral circulation: the main arteries supplying the brain are the two internal carotid arteries and basilar artery. When the main arteries join the connecting arteries, they will form the circle of Willis. Circle of Willis enables the regulation of blood flow and BP within the brain. From the brain: the blood into sinuses(wide vessels) and return to the main circulation at the internal jugular
Spinal circulation: the spinal cord is nourished by the 3 main arteries and an arterial network. The 3 main arteries are: the anterior spinal artery , the vertebral artery and subclavian arteries.
