nervous system
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main components of the nervous system
neurons, brain and spinal cord
nervous system can be divided into
central (brain and spinal cord) and peripheral nervous system (nerves/neuron)
spinal cord is made of and extends from and contains, length
nervous tissue foramen magnum and terminates at a structure called conus medullaris cerebrospinal fluid 43-45cm
brain consists of
cerebrum, cerebellum and brainstem
cerebrum is divided into 4 lobes
Temporal, Occipital, Parietal and Frontal
frontal lobe function
problem solving emotional traits judgement speaking voluntary motor action
temporal lobe function
understanding language behaviour memory hearing
parietal lobe function
knowing left from right sensation reading body orientation
occipital lobe function
vision colour perception
cerebellum function
balance coordination + control of voluntary movement fine muscle control
spinal cord function
receiving signals from the brain which translates into motor and autonomic function, sends sensory signals to the brain such as touch, pressure, temperature etc. The spinal cord can act independent of the brain in cases of motor reflexes (patellar reflex)
brain stem function
breathing body temp digestion sleep swallowing
peripheral nervous system consists of
somatic and autonomic nerves
Somatic nerves are related to
movement (responses via skeletal muscles)
autonomic is divided into
sympathetic and parasympathetic nerves (responses via glands, smooth and cardiac muscles)
autonomic is related to
internal organs
Description of a neuron
cell body that contains nucleus and cytoplasm and contains cell processes namely dendrites and axons length of a neuron is dependent on the type and location of the neuron in the body. The excitability factor of a neuron makes them suited for communication, thus they respond to stimuli by producing an electrical signal
charge difference across the plasma membrane of a neuron
-70millivolts (resting membrane potential)
produce an action potential
voltage difference across the neuron plasma membrane needs to be shifted by the minimum amount (threshold). The threshold is usually reached by when the plasma membrane of a neuron has voltage-sensitive sodium ion channels
three main types of neurons
Sensory neurons (Afferent): receives information from sensory receptors (i.e., eye and skin), which is relayed to the brain and spinal cord. - Interneurons: situated in the brain and spinal cord and send information to other neurons - Motor neurons (Efferent): carries info received from the interneuron to the effector (muscles and glands) for effect
Features of an Action potential
• The re-excitability of a neuron cannot occur until the resting membrane potential is restored • Action –potentials are “all or nothing” • Induces the release of neurotransmitters (i.e. acetylcholine, adrenaline) across a synapse (narrow gap between the output zone and input zone of another neuron)
Nerve pathways
Nerves are long distance lines that connect the CNS to the rest of the body; myelin sheath encapsulates the axon of nerves providing insulation which enables faster propagation of impulses
Myelin sheath is made of
oligodendrocytes In the brain whilst in the rest of the body, it is made of Schwann cells
Reflexes
simplest nerve pathways, sensory and motor neurons take part in automatic responses aka reflexes. Reflexes are simple automatic responses to stimuli