Nervous system, endocrine system, Homeostatis Flashcards
Systems contributing to coordination
nervous system and the endocrine system.
Fore brain consists of
Cerebrum, thalamus, hypothalamus and pineal body
Hind brain consists of
Cerebellum, pons varolli and medulla oblongata
Cerebro-ventricles
Central canal of the brain forms 4 irregular shaped cavities called ventricles. Three ventricles are present in the forebrain and 1 in the hind brain.
Central canal and ventricles are filled with cerebro-spinal fluid.
Functions of cerebrospinal-spinal fluid
Maintains uniform pressure within the CNS.
Acts as a shock absorber between brain and the skull
Circulates nutrients, hormones as well as to remove waste matter.
Protection of CNS
Brain is enclosed by a skull while the spinal cord is surrounded by the vertebral column.
Further protection is given by 3 meninges known as dura matter (outermost), Pia matter (innermost) and in between the arachnoid matter.
Thalamus
Located in the cerebral hemisphere just below the corpus callosum.
Acts as the main input centre for sensory information from special sense organs and sensory receptors in the skin and integral organs. These sensory information are sent to specific locations in the cerebral cortex for further processing.
It mainly relays and redistribute nerve impulses from most parts of the brain to the cerebral cortex.
Hypothalamus
Located below and infront of the thalamus immediately above the pituitary gland.
Connected to the posterior lobe of the pituitary gland by nerve fibres and to the anterior lobe of the pituitary gland by a complex system of blood vessels.
Regulates body temperature Regulates thirst and water balance Regulates appetite Regulates sleep and wake cycles Control of autonomic nervous system Initiates fight or flight response Plays a role in sexual behaviour Source for posterior pituitary hormones and releasing hormones that acts on anterior pituitary
Mid brain
Mid brain is the upper part of the brain stem. Situated between the cerebrum above and pons varolli below surrounding the crebro-spinal fluid filled connections of the 3rd and the 4th ventricles.
Acts as a relay station for ascending and descending nerve fibres
Receives and integrates sensory information (auditory and visual) and sends it to particular regions of the forebrain
Coordinates auditory and visual reflexes
Pons varoli
Situated infront of the cerebellum below the midbrain and above the medulla oblongata
Transfer information between the PNS and the forebrain and midbrain
Coordinates large scale body movements climbing and running
Together with the medulla oblongata helps regulate respiration
Medulla Oblongata
Lowest part of the brain stem situated below the pons varolli and is continuous with the spinal cord. Consists of respiratory center, cardiovascular center and reflex centres.
Transfer information between the PNS and the forebrain and midbrain.
Coordinates large scale body movements such as running and climbing.
Controls several autonomic, homeostatic functions including breathing, heart and blood vessel activities.
Controls involuntary reflexes such as vomiting, swallowing, coughing, sneezing through reflex centres.
Cerebellum
Located behind the pons varoli and below the posterior part of the cerebrum
Coordinates voluntary muscle movements
Maintains posture and balance
Helps in learning and remembering motor skills
Spinal cord
I the spinal cord outer region is composed of white matter while the inner region is composed of grey matter
Links the CNS to sensory neurones and motor neurones and facilitates nerve impulse propagation towards the brain and away from the brain.
Coordinates and produces reflexes
Antagonistic
Opposite
2 divisions of autonomic nervous system
Sympathetic stimulations prepare the body to deal with exciting/stressful and energy generating situations (fight of flight)
Parasympathetic division causes opposite responses that promote calming or return to self-maintenance functions (rest and digest)
Parasympathetic nerves exit the CNS at the base of the brain and spinal cord as cranial nerves or spinal nerves respectively. On the other hand sympathetic nerves exit only from the spinal cord.
Constricts pupil of the eye
Parasympathetic
Inhibits salivary gland secretion
Sympathetic
Constricts bronchi in lungs
Parasympathetic
Accelerates heart
Sympathetic
Stimulates activity of the stomach and intestine
Parasympathetic
Inhibits activity of the pancreas
Sympathetic
Stimulates gall bladder
Parasympathetic
Stimulates adrenal medulla
Sympathetic
Promotes emptying of bladder
Parasympathetic
Promotes ejaculation and vaginal contractions
Sympathetic
Resting potential
When a neurone is at rest (not sending a signal/non conducting) the membrane potential is called the resting membrane potential. -60 mV to -80mV
Maintained by the distribution ion concentrations inside and outside of the cell
Concentration of K+ is higher inside the cell while the concentration of Na+ is higher outside the cell. In addition Cl- and large proteins anions are present inside the cell. Due to this there is a relative negative charge inside the cell and a positive charge outside the cell.
Selective permeability of the membrane to K+ and Na+ ions
There are more potassium channels open than sodium channels. As a result there is a net negative charge inside the cell.
Sodium-pottasium pump
This pump transports 3 Na+ out of the cell for every 2 K+ that is transports in. This pump uses ATP to actively transport these ions.
Action potential
An action potential occurs due to the change in the membrane potential above a threshold level due to a stimulus. Consists of depolarization, repolarization and hyperpolarization.
Depolarization
A change in the membrane potential such that inside of the cell is made less negative relative to the outside. Depolarization results due to Na+ inflow in response to a stimulus.
Repolarization
Sodium channels close blocking the inflow of Na+. However most potassium channels open permitting K+ outflow making inside of the cell negative.
Hyperpolarization
Sodium channels are closed but potassium channels are opened. As a result inside of the cell becomes more negative.
Refractory period
Short time immediately after an action potential in which the neuron cannot respond to another stimulus, owing to the inactivation of sodium channels. This prevents reverse conduction of an impulse in an axon.
Conduction of a nerve impulse
A series of action potentials that move along an axon is known as a nerve impulse
Axon potential spreads to the neighbouring location while the initial location repolarizes
The speed of conduction depends on
Conduction speed increases with the diameter of the axon
Precense of myelinated axon
Synapses
A synapse is a junction where a neurone (presynaptic cell) communicates with a postsynaptic cell across a narrow gap (synaptic cleft).
Neurotransmitter
Neurotransmitters are molecules secreted at synaptic terminals of presynaptic neuron, diffused across synaptic cleft, bind to receptors at the postsynaptic membrane, triggering a response.
Common neurotransmitters
Acetylcholine Some amino acids Biogenic amines Neuropeptides Some gases