The Human Nervous System Flashcards
What are the subdivisions of the human nervous system?
Central and peripheral
Central nervous System
Brain and spinal cord
Peripheral Nervous system
Cranial nerves and associated sensory ganglia; Spinal nerves, dorsal root ganglia and autonomic ganglia
- Somatic nervous system
- Autonomic nervous system
- both have an afferent division and efferent division
Divisions of the Peripheral Nervous System
Somatic Nervous System- the nerves that convey messages from the sense organs to the CNS and from the CNS to the skeletal muscles
-Autonomic Nervous System- a set of neurons that control the heart, the intestines, and other organs
Functions of the Nervous System
Sensory- monitors internal & external environment through presence of receptors
- Integration: interpretation of sensory information; complex functions
- Motor: response to information processed through stimulation of effectors (-muscle contraction, glandular secretion
Spinal Cord
- It is a vital link between the brain and the body and from the body to the brain
- The spinal cord extends from the foramen magnum where it is continuous with the medulla to the level of the first or second lumbar vertebrae
Somatic and Autonomic
The somatic nervous system composed of somatic parts of the CNS and PNS provides sensory and motor innervation to all parts of the body
- The autonomic nervous system (ANS) classically described as the visceral nervous system or visceral motor system
Description of the Somatic Nervous System
- Somatic senses ( pain, thermal, tactile, proprioreceptive)
- Somatic motor neurons-skeletal muscle
- Usually voluntary
- Motor units
- Acetylcholine
Description of Autonomic Nervous System
Autonomic sensory (chemoreceptors, mechano-receptors
- Motor neurons regulate visceral activities
- Preganglionic and postganglionic neurons
- Acetylcholine or norepinephrine
Autonomic Nervous System
- The efferent nerve fibers and ganglia of the ANS are organized into two systems or division:
- the sympathetic ( thoracolummbar) and the parasympathetic ( craniosacral) division
Different types of ganglia
*Sympathetic: Sympathetic trunk- innervate organs above the diaphragm; superior, middle, inferior cervical ganglia
Prevertebral- below the diaphragm; celiac, superior, and inferior mesenteric ganglia
*Parasympathetic:
Preganglionic axons are larger than in sympathetic ganglia; Preganglionic neurons are myelinated, postganglionic neurons are not
Action by neurotransmitters in ANs
- Acetylcholine (cholinergic neurons): All preganglionic, sympathetic postganglionic innervation of sweat glands, all parasympathetic postganglionic neurons, nicotinic, muscarinic receptors
- Norepinephrine ( adrenergic): alpha and beta receptors; can be excitatory or inhibitory
Functions of ANS
- “Fight or flight” (sympathetic): more widespread and longer lasting; norepinephrine and epinephrine can act as hormones as well as neurotransmitters
- “Rest and digest” (parasympathetic): salivation, lacrimation, urination, digestion, and defecation
Control of Autonomic Functions
- Reflexes: blood pressure, digestion, defecation and urination
- Control within brain: Brain stem ( cardiovascular, swallowing, digestion)
Embryology of the Nervous System
- The nervous system including the spinal cord, brain, and peripheral nerves is derived from ectoderm
- The primordial structure which gives rise to the nervous system appears around day 1 of development
- The CNS is formed in week 3 of development
- The neural plate gives rise to the brain and spinal cord
- Neurulation is the transformation of the ectoderm overlying the notochord into a neural tube, which is flanked by 2 longitudinal formations, the neural crests: the rostral part of the neural tube becomes the adult brain; the caudal part of the neural tube becomes the adult spinal
