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Chapter 7 - Part 3 The Nervous System. The Reflex Arc  Reflex – rapid, predictable, and involuntary responses to stimuli  Much like a one-way street.

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Presentation on theme: "Chapter 7 - Part 3 The Nervous System. The Reflex Arc  Reflex – rapid, predictable, and involuntary responses to stimuli  Much like a one-way street."— Presentation transcript:

1 Chapter 7 - Part 3 The Nervous System

2 The Reflex Arc  Reflex – rapid, predictable, and involuntary responses to stimuli  Much like a one-way street – once a reflex begins, it always goes in the same direction  Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector  The neural pathway where reflexes occur over

3 Simple Reflex Arc

4 Types of Reflexes and Regulation 1.Autonomic reflexes  Regulate the activity of smooth muscles, the heart, and glands.  Regulate digestion, elimination, blood pressure, and sweating.  Examples: Secretion of saliva and changes in the size of the eye pupils. 2.Somatic reflexes  Include all reflexes that stimulate the skeletal muscles.  Examples: When you pull your hand away quickly from a hot object.

5 CNS  During embryonic development, the CNS first appears as a simple tube, the neural tube  The neural tube becomes the brain and spinal cord  The opening of the neural tube enlarges and becomes the ventricles or chambers  Four chambers within the brain  Filled with cerebrospinal fluid

6 The Brain It weighs a little over 3 lbs. It looks wrinkled like a walnut and with the texture of cold oatmeal. Largest and most complex mass of nervous tissue in the body.

7 Regions of the Brain 1.Cerebral hemispheres 2.Diencephalon 3.Brain stem 4.Cerebellum

8 Cerebral Hemispheres (Cerebrum)  Paired (left and right) superior parts of the brain  Include more than half of the brain mass  Encloses and obscures much of the brain stem  How a mushroom cap covers the top of the stalk

9 Cerebral Hemispheres (Cerebrum)  The surface is made of elevated ridges (gyri) and shallow grooves (sulci)

10 Lobes of the Cerebrum  Fissures (deep grooves) divide the cerebrum into lobes  Surface lobes of the cerebrum 1.Frontal lobe 2.Parietal lobe 3.Occipital lobe 4.Temporal lobe

11 Lobes of the Cerebrum

12 Specialized Areas of the Cerebrum  Somatic sensory area – receives impulses from the body’s sensory receptors  Located in the parietal lobe  Allows you to recognize pain, coldness, or a light touch  The body is represented in an upside down manner in the sensory area  The sensory pathways are crossed – the left side of the cortex receives impulses from the right side of the body

13 Sensory and Motor Areas of the Cerebral Cortex

14 Specialized Areas of the Cerebrum  Impulses from the special sense organs are interpreted in other cortical areas.  Visual area  Located in the posterior part of the occipital lobe  Olfactory area  Located deep inside the temporal lobe

15 Specialized Areas of the Cerebrum  Primary motor area – sends impulses to skeletal muscles  Allows us to consciously move our skeletal muscles  Located in the frontal lobe  The body is represented upside-down  Pathways are crossed  Most of the neurons in the this primary motor area control body areas having the finest motor control (face, mouth, hands)

16 Specialized Areas of the Cerebrum  Broca’s area – involved in our ability to speak  Damage to this area causes inability to say words properly (you know what you want to say, but you can’t vocalize the words)

17 Specialized Areas of the Cerebrum  Higher intellectual reasoning – believed to be in the anterior part of the frontal lobe  Complex memories – Appear to be stored in the temporal and frontal lobes  Language comprehension (word meanings) – located in the frontal lobes  Speech Area – allows one to sound out words  Located at the junction of the temporal, parietal, and occipital lobes

18 Layers of the Cerebrum  Gray matter  Outer layer  Composed mostly of neuron cell bodies  Cerebral cortex – the outermost gray matter of the cerebrum

19 Layers of the Cerebrum  White matter  The remaining, deeper cerebral hemisphere tissue  Composed of fiber tracts (bundles of nerve fibers) carrying impulses to or from the cortex  The corpus callosum (large fiber tract) connects the cerebral hemispheres  Allows the cerebral hemi- spheres to communicate with one another

20 Layers of the Cerebrum  Although most of the gray matter is in the cerebral cortex, there are several islands of gray matter buried deep within the white matter.  Basal nuclei – internal islands of gray matter  Help regulate voluntary motor activities by modifying sent instructions  Individuals who have problems with their basal nuclei are often unable to walk normally or carry out other voluntary movements.  Examples: Huntington’s disease and Parkinson’s disease

21 Diencephalon  Sits on top of the brain stem  Enclosed by the cerebral hemispheres  Made of three parts 1.Thalamus 2.Hypothalamus 3.Epithalamus

22 Diencephalon

23 Thalamus  Surrounds the third ventricle  The relay station for impulses  Transfers impulses to the correct part of the cortex for localization and interpretation

24 Hypothalamus  Under the thalamus  Important autonomic nervous system center  Helps regulate body temperature  Controls water balance  Regulates metabolism

25 Hypothalamus  Center for many drives and emotions  An important part of the limbic system (emotions)  Thirst, appetite, sex, pain, and pleasure centers are in the hypothalamus  Regulates the pituitary gland (endocrine organ) and produces two hormones of its own.  The pituitary gland hangs from the anterior roof of the hypothalamus by a slender stalk.

26 Epithalamus  Forms the roof of the third ventricle  Houses the pineal body (an endocrine gland)  Includes the choroid plexus – knots of capillaries within each ventricle that forms the cerebrospinal fluid

27 Brain Stem  Attaches to the spinal cord  About the size of a thumb in diameter and approximately 3 inches long  Functions: 1.Provide a pathway for ascending and descending tracts 2.Has many small gray matter areas (form cranial nerves and control many vital activities)  Parts of the brain stem: 1.Midbrain 2.Pons 3.Medulla oblongata

28 Brain Stem Slide 7.38b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.15a

29 Midbrain  Mostly composed of tracts of nerve fibers  Composed primarily of two bulging fiber tracts – cerebral peduncles (literally, “little feet of the cerebrum”)  Function is to convey ascending and descending impulses  Has four rounded protrusions – corpora quadrigemina  These bulging nuclei are reflex centers involved with vision and hearing

30 Pons  The bulging center part of the brain stem  Mostly composed of fiber tracts  Includes nuclei involved in the control of breathing

31 Medulla Oblongata  The lowest part of the brain stem  Merges into the spinal cord  Is an important fiber tract area  Contains important control centers  Heart rate control  Blood pressure regulation  Breathing  Swallowing  Vomiting

32 Reticular Formation  Diffuse mass of gray matter along the brain stem  Involved in motor control of visceral organs  Reticular activating system (RAS) plays a role in awake/sleep cycles and consciousness  Damage to this area can result in permanent unconsciousness (coma)

33 Reticular Formation Slide 7.42b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.15b

34 Cerebellum  Projects dorsally from under the occipital lobe  It has two hemi- spheres and a convoluted surface  Has an outer cortex made up of gray matter and an inner region of white matter

35 Functions of the Cerebellum  Involuntary  Provides the precise timing for skeletal muscle activity and controls our balance and equilibrium  Makes our body movements smooth and coordinated

36 Damage to the Cerebellum  If the cerebellum is damaged, movements become clumsy and disorganized.  Cannot keep their balance and appear to be drunk because of the loss of muscle coordination.  They are no longer able to touch their finger to their nose with their eyes shut.

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