UNIT 5: Nervous System – part 4 THE HUMAN BRAIN

1. UNIT 5: Nervous System – part 4THE HUMAN BRAIN

3. Protective Structures • The brain and spinal cord are delicate and vital organs and are protected by two coverings 1. Outer bone coverings 2. Inner membranes called the “meninges” • Between the bone & the meninges: protection = cerebrospinal fluid • Cushions & nourishes the brain & spinal cord

5. Meninges • Consists of 3 layers • Dura mater – “Tough Mother” • Outer layer • Made of a thick fibrous tissue • Also has extensions which separate parts of the brain • Arachnoid mater • Middle layer • Delicate, cobweb like-layer • Pia mater • Innermost layer • Transparent and adheres to blood vessels on the outer surface of the brain and spinal cord

7. Meningitis • An infection or inflammation of the meninges is called meningitis • Usually caused by bacteria but could also be viral or the result of a tumor • Generally affects the arachnoid mater or the pia mater • Symptoms include fever, severe headaches, neck stiffness, and pain • Meningitis may range from a mild condition to a fatal illness

8. Brain Facts • The brain is one of the largest organs in the adult human body • It weighs about 3 lbs. • Also contains about 100 billion neurons and 900 billion glial cells  • The brain grow rapidly through the first 9 years, attains full size by the 18th year

9. Parts of the Brain: • The brain has 4 main regions: • CEREBRUM • CEREBELLUM • BRAIN STEM • DIENCEPHALON

10. 1) CEREBRUM:  Divided into hemispheres (R and L) Each hemisphere divided into lobes (frontal, parietal, temporal, occipital) • Each hemisphere has a highly folded outer covering of gray matter = CEREBRAL CORTEX • Hemispheres are connected by white matter called CORPUS CALLOSUM

14. CEREBRUM – functions! • Where memories are stored • Interprets sensory impulses arriving from sense organs  Centers for motor coordination; send motor impulses to muscles • Where conscious decisions are made • Intelligence and personality stem from cerebral activity

15.  2 functional cortical areas: 1) Motor Cortex: sends commands to skeletal muscles

17. 2) Somatosensory Cortex: *Receives and integrates signals from touch, pain, pressure, and temperature receptors; *Divided into specific areas so that we can associate specific stimuli with specific parts of the body. 

20. 3) Association Areas: • Neither primarily motor nor sensory • they connect with one another and with other brain areas • Analyze & interpret sensory experiences • Oversee memory, reasoning, verbalizing, judgment, & emotion • Ex: association areas of the frontal lobe control many higher intellectual processes vs. assoc. areas in occipital lobes deal with visual interpretation

22. Language • Language functions consist of the ability to speak and write words, and the ability to understand spoken and written words. • Broca’s area is a large speech center located in the frontal lobe • Damage to Broca’s area would cause a person to be unable to articulate words, but still make vocal sounds and understand written and spoken language • Wernicke’s area is located posteriorly in the temporal lobe • This area is responsible for understanding written and spoken language

24. Specialization of Cerebral Hemispheres • The right and left hemispheres of the cerebrum specialize in different functions • The left hemisphere: language functions, and dominates hand movements (especially skilled gestures and movements) • Most of the population uses their right hands • The right hemisphere: perception of certain auditory stimuli, tactual perception, and in perceiving and visualizing spatial relationships • Despite specializations in each hemisphere, both hemispheres communicate with each other through the corpus collosum

25. 2) CEREBELLUM: coordination of movement; balance; hand-eye coordination

26. 3) BRAINSTEM: • superior end of spinal cord; • 3 parts that function in: -HOMEOSTASIS -Movement coordination -Conduction of info. to higher brain centers:

27. 1) Medulla oblongata: controls involuntary reflexes like breathing, heart and blood vessel activity, swallowing, vomiting, digestion

28. 2) Pons: regulates breathing centers in the medulla oblongata

29. 3) Midbrain: receives and sends sensory information that coordinates eye movements/head movements to respond to stimuli

30. 4) DIENCEPHALON (Between Brain): • Located between the cerebral hemispheres and above the midbrain. • Includes the: • thalamus • hypothalamus • optic tracts & optic chiasma • posterior pituitary gland • pineal gland

32. THALAMUS: relay center that sorts out & transmits sensory info. to and from cerebrum

33. HYPOTHALAMUS:  Important regulator of HOMEOSTASIS  Contains body’s thermostat (regulates temperature)  Includes centers for regulating hunger & thirst  Plays role in sexual response and mating behavior Fight-or-flight response, pleasure, daily biorhythms

37. Pineal Gland (Body) • Located below the hypothalamus and named pineal gland because its structure resembles a small pinecone • Functions of the pineal gland are not well understood but it is thought to be involved in regulating the body’s biological clock • Produces the hormone melatonin, which is thought to synchronize various body functions with each other and external stimuli

38. Optic Chiasma • Region where the right and left optic nerves cross each other before entering the brain