The Nervous System
composed of neurons
axon- threadlike projection of cell body
carries signal away from cell body
dendrites- receives signal from preceding neuron
Nerve- bundle of axons
Central Nervous System (CNS)- brain and spinal cord
Peripheral Nervous System (PNS)- other nerves
afferent neurons- collect info from body and transmit toward
CNS
efferent neurons- transport info from CNS to body
Brain
~1.4 kg, or 2% total body weight, 100 billion neurons
Cerebrum- largest part of brain
2 hemispheres divided by corpus callosum- axons
Cerebral cortex- folded outer layer
sensory (auditory, visual, body sensation) processing and
motor responses
`White matter- beneath cortex
axons of cortical neurons
links regions of cortex with each other
Thalamus- directs incoming sensory signals to proper region of
cerebral cortex
Limbic system- emotion, memory, motivation
Brain stem- links cerebrum with spinal cord
Midbrain- relays visual and auditory info
Pons- relay between hemispheres and cerebellum
Medulla oblongata- control homeostasis, heart rate
Reticular formation- controls respiration
Cerebellum- coordinates of muscle action, timing muscle
contractions
Spinal Cord
Column of nervous tissue starting in medulla oblongata thru
vertebral column
White matter surrounds grey matter (cell bodies)
Peripheral Nervous System
Sensory receptor- detects stimulus
Motor neuron- contact and carry info to muscles and glands
Interneurons- connect other neurons to each other
2 divisions
Somatic NS- controls mvmt of skeletal muscles
Autonomic NS- controls body's internal conditions by
controlling smooth muscles
Sympathetic- physical and emotional stress
Parasympathetic- routine conditions
How are impulses transmitted across nerves?
potential- difference in electrical charge
At rest- negative charge inside, positive outside
Electrical impulse travels by reversing charge
Sense Organs
Mechanoreceptors-movement, pressure, tension
Photoreceptors- light
Chemoreceptors- chemicals
Thermoreceptors- changes in temp
Pain receptors- tissue damage
Hearing (auditory)
Vision
Taste
Smell (olfactory)
Touch
Endocrine System
Ductless glands located thruout body
(Exocrine glands have ducts)
"Gland" organ that secretes materials into other regions of the body
Hormones:
Amino-acid based hormones - ex. adrenaline
Steroid hormones- synthesized from cholesterol- ex. testosterone
Glands:
Pituitary- secretes hormones that affect other glands and organs
regulated by the hypothalamus, in the brain
Primary regulatory of endocrine system
Thyroid- located below larynx in neck
regulates heart rate, blood pressure, body temp, metabolism
Adrenal- located above each kidney
fight or flight
salt and water balance
Gonads- release sex hormones
Pancreas- Islet of Langerhans- insulin and glucagon
Reproductive System
Males:
Testes- produce sperm
Seminiferous tubules, scrotum
Epididymis- tube to travel
vas deferens- duct to abdominal cavity to join with urethra
Semen- nutritive and protective fluid produced by seminal
vesicles, bulbourethral glands, prostate gland
Ejaculation- release of semen/sperm thru penis
Females:
ovaries- produce eggs (ovum)
fallopian tube- hollow tube that connects ovaries to uteris
uterus- site of embryonic development
cervix- lower entrance to uterus
vagina- muscular tube leading to the outside of the body
Menstrual Cycle:
Monthly preparation for pregnancy
approximately 28 days- hormones progesterone and estrogen
control cycle
Uterus lining thickens with blood vessels to nourish embryo
Egg matures, enters fallopian tubes, travels to uterus
if egg is fertilized in fallopian tube, will implant in uterus
Menstruation- if egg is unfertilized, lining of uterus sloughs
