HUMAN ANATOMY-4 Nervous system. Endocrine system.
General info There are 2 body systems, which maintain internal coordination of trillions of cells: nervous system and endocrine system. Nervous system sends electrical & chemical messages to cells Endocrine system works by means of hormones, secreted to the blood.
Nervous system – general info Nervous System (NS) consists of 2 types of cells: cell of nervous tissue - NEURON & cell of connective tissue – GLIAL CELL. So the nervous system is the mixture of two types of tissue, called neuroglia (p.164, fig.5,24).
Neuron Neuron, apart from its common for majority of other cells general cellular compartments, has 2 types of extensions: DENDRIT & AXON. Dendrit – is a short and intensively branched extension, which receives signals from other cells. Axon – is the long (sometimes up to the 1 m or more) extension, which sends outgoing signals to the cells.
NEURON – physiologic properties These characteristics allow neurons to communicate. Exitibility – they response to environmental stimuli Conductivity – produced electrosignals propagate to various distances Secretion – nerve endings secret neurotransmitters, that stimulates other cells.
NEURON – functional classes (p.442, fig.12.3). – sensory (afferent) neurons, present within organs to detect stimuli & send them to CNS – motor (efferent) neurons, send signals from CNS to muscles & glands for action – interneurons, comprise 90% of all neurons, present only in CNS.
Glial cell Glial cells occupy the most part of nervous system Their major function is to support & protect nervous cells. They resemble connective tissue cells and don’t transmit signals for long distances.
Central & peripheral nervous systems Neuroglia comprises nervous system, which consists of 2 departments: Central Nervous System (CNS) & Peripheral Nervous System (PNS) (p.440, fig.12.1). CNS is presented by 2 subdivisions: BRAIN, located within the cranium, & SPINAL CORD (located within vertebral channel)
CNS & PNS – functional classification PNS consists of 2 subdivisions: SENSORY subdivision, which receives signals and MOTOR subdivision, which sends outgoing signals. Each of this parts has visceral (involuntary) and somatic (voluntary) parts. Besides that visceral motor subdivision is comprised of SYMPATHETIC & PARASYMPATHETIC compartments (p.441, fig. 12.2).
Autonomic nervous system The sympathetic division tends to arouse the body for action, dominates at the daytime (& inhibit digesition) The parasympathetic division tends to have a calming effect, dominates at the nighttime (& stimulate digestion) Common name for these divisions is autonomic nervous system
SPINAL CORD (p.480, fig.13.1) Is a cylinder of nervous tissue, which spreads from the brain upto the 1 st lumbar vertebra Gives rise to 31 pairs of spinal nerves Has 4 regions: cervical (C1 – C8), thoracal (T1 – T12), lumbar (L1 – L5) & sacral (S1 – S5)
BRAIN (p.513 fig.14.1) Consists of 3 major parts: cerebrum, cerebellum, brainstem. Cerebrum is the highest center for control of body functions & behavior Proportions of body parts on motor cortex of the brain (p.542 fig.14.23). Cerebellum provides with balance & coordination Brainstem provides with breathing & heart beating centers. 12 pairs of cranial nerves arise from the brainstem.