Chapter 2: The Systems of the Body
The nervous system is a complex network of interconnected nerve fibres that regulate important bodily
functions, including response to and recovery from stress.
- Sensory nerve fibres -> input to the brain and spinal cord by carrying signals from sensory receptors
- Motor nerve fibres -> output from the brain and the spinal cord to muscles and other organs -> re-
sults in voluntary and involuntary movement.
- CNS: brain + spinal cord
- PNS: nerves that connect to the brain and the spinal cord
- Somatic nervous system: VOLUNTARY
- connects nerve fibres to voluntary muscles.
- provides brain with feedback as sensory information, about the voluntary
- Autonomic nervous system: INVOLUNTARY
- connects central nervous system with all the internal organs, the organs that
- Sympathetic nervous system: reactions to stress
- prepares the body to response to emergencies
- to strong emotions
- to strenuous activity
- called a catabolic system because it is concerned with the
mobilization and exertion of energy.
- Parasympathetic nervous system: activities of organs under normal
- after an emergency, restores the body to a normal state
- conservation of body energy = anabolic system
The brain is the command centre of the body
- receives afferent/sensory impulses from the peripheral nerve endings
- sends efferent/motor impulses to the extremities and to internal organs
- heavily responsible for regulation of heart rate, blood pressure, and respiration
- medulla- rate at which the heart is contracting, speeds up, slows down
- receives sensory information about blood pressure (and based on that),
- constriction or dilation of blood vessels
- sensory information about the levels of O2 and CO2,
- controls rate of breathing
- pons- link between hindbrain and midbrain
- helps control respiration
- cerebellum- coordinates voluntary muscle movement 2
- maintenance of balance and equilibrium, muscle tone and pressure
- damage results in troubles coordinating muscles effectively
- and produces lack of muscle tone, disturbances in posture of gait
- specifically is responsible for the coordination of visual and auditory reflexes
- major pathway for sensory and motor impulses b/w forebrain and hindbrain
- diencephalon: thalamus + hypothalamus
- Thalamus - recognition of sensory stimuli
- relay of sensory impulses to the cerebral cortex
- Hypothalamus - regulates the medulla
- regulating water balance and appetites (hunger + sexual desire)
- transition between thoughts and actual actions; ex: embarrassment ->
blushing via the hypothalamus.
- w/ pituitary gland regulates the endocrine system-> releases hormones
- telencephalon: composed of both the hemispheres of the cerebral cortex
- cerebral cortex: largest portion of the brain; intelligence, memory, personality
- sensory impulses are interpreted here
- motor impulses pass down from the cortex to lower brain, and then to
other parts of the body.
- four lobes: frontal, parietal, temporal, and occipital (each has own
memory storage area)
- frontal: motor cortex, coordinates voluntary movement; the left
part controls the activities of the voluntary muscles on the right
side of the body, and vice versa.
- parietal: somatosensory cortex;
- sensations of touch, pain, temperature, and pressure are
registered and interpreted
- temporal: cortical areas responsible for auditory and
- occipital: visual cortex; receives visual impulses
- basal ganglia: four round masses embedded deep in the
cerebrum (main portion); smooth motor coordination
The Limbic System: 3
- the structure borders the midline of the brain; stress and emotional responses.
- amyglada: detection of threat
- hippocampus: emotionally charged memories.
- cingulate gyrus, septum, areas in the hypothalamus - related to emotional functioning.
- interior of thalamus, nuclei within hypothalamus are important for socially relevant behaviours.
Neurotransmitters: chemicals that regulate nervous system functioning. Stimulation of sympathetic ner-
vous system -> secretion of epinephrine and norepinephrine (together catecholamines) -> enter blood-
stream -> carried throughout the body promoting activity of sympathetic stimulation.
Catecholamines released :
-> increased heart rate, heart’s capillaries dilate, blood vessels constrict
-> blood pressure goes up.
-> Blood is diverted into muscle tissue.
-> Respiration rate goes up - amount of inspiration increases.
-> digestion and urination decreased
-> pupils of the eyes dilate
-> sweat glands are stimulated
Repeated arousal of the sympathetic nervous system leads to implications for the development of several
chronic disorders, such as coronary heart disease, and hypertension.
Parasympathetic functioning restores the homeostasis in the body.
Disorders of the nervous system:
Epilepsy: idiopathic; no specific cause for the symptoms.
- it is marked by seizures
EVENT OR A STRONG EMOTION