THE CENTRAL NERVOUS SYSTEM The Brain & Spinal Cord
Review: Nervous System
Parallel Distributed Processing
Composition of the CNS Nuclei: Clusters of neurons in the CNS ( neighborhoods ) Fiber Tracts/Pathways: Bundles of axons that travel together ( highway )
The Spinal Cord Receives signals from the senses & relays them to the brain. Neurons in the SC also carry signals from the brain to the muscles. Sensory Neurons: Afferent neurons that carry signals TO the brain (arrive) Motor Neurons: Efferent neurons that carry information FROM the brain. (exit)
Spinal Cord Also direct simple behaviors called reflexes: simple, automatic movements.
Interesting facts about the CNS! The adult human brain weighs about 3 lbs. The human spinal cord is 45 cm long in men and 43 cm long in women.
3 Major Divisions of the Brain The Hindbrain The Midbrain The Forebrain Cerebral Cortex
The Hindbrain
The Hindbrain Location Lies just inside the skull Continuation of the SC & makes up part of the brain stem. Signals coming from the SC reach the hindbrain first. Function Nuclei in the HB control vital autonomic functions. Including blood pressure, heart rate & breathing. Associated Parts Medulla (Oblongata), Reticular Formation, Locus Coeruleus, Cerebellum & Pons.
Hindbrain: The Medulla (Oblongata) Location Function Lies below the Pons Controls automatic functions BP, HR, breathing, digestion, etc.
Hindbrain: Reticular Formation Location Function Network of cells threaded throughout the HB & MB. Responsible for consciousness, awareness, arousal, attention. Filters sensory input.
Hindbrain: Locus Coeruleus Blue Spot Location Function Small nucleus located in the R.F. Involved in directing attention.
Hindbrain: Cerebellum ( little brain ) Location Function Connected by the brain stem to the SC at the base of the skull. Coordination of movement & balance. Related to other behaviors not directly related to physical movement.
Hindbrain: Pons ( bridge ) Location Directly below the midbrain. Connects the medulla to the cerebral cortex & cerebellum. Helps send information to other parts of the brain. Function Involved in sleep & arousal. Manufactures chemicals involved in sleep.
The Midbrain
The Midbrain Location Very small structure directly above the HB and below the forebrain. Along with parts of the HB, the MB makes up the brain stem. Function Integrates sensory information w/ simple, reflexive movements. Associated Parts Substantia Nigra
Midbrain: Substantia Nigra ( Black Substance ) Area of pigmented cells at the top of the midbrain region. Location Connected to the striatum in the forebrain. Function Produces & uses dopamine (a NT involved in movement & other functions). Along with the striatum, helps smoothly begin movement. May be linked to mood & addiction.
The Forebrain
The Forebrain Location Upper region of the brain. The largest & most complex part of the brain, which folds back over & completely covers other parts of the brain. Function Responsible for the most complex aspects of behavior. Associated Parts Striatum, hypothalamus, thalamus, suprachiasmatic nuclei, amygdala, hippocampus. Some of these parts are part of the limbic system.
The Limbic System Located under the cortex region of the brain and above the brain stem. Responsible regulating: Memories Motivation (hunger, sex, thirst) Emotion
Forebrain: Thalamus
Forebrain: Thalamus Location Function Above the brain stem. Relay station for all sensory information (except smell). Processes sensory info from SC & sends the info to the cerebral cortex.
Forebrain: Hypothalamus
Forebrain: Hypothalamus Location Function Lies underneath the thalamus & connects to many other brain regions. Regulator of biological needs. Regulates hunger, thirst, body temp, sex drive, etc. Links to the endocrine system & controls the pituitary gland. Function Contains the suprachiasmatic nuclei: the brain s time piece. Establishes a 24 hour clock that maintains biological rhythms.
Forebrain: Amygdala Location Function An almond shaped structure that lies within the temporal lobe of the brain a few inches from the ear. Emotional and social processing. Particularly fear. Memory processing & decision making.
Forebrain: Hippocampus
Forebrain: Hippocampus Location Located deep within the temporal lobe. Extends from the amygdala. Function Associated with the formation of new memories. Also appears to send memories into the cerebral cortex for long term storage.
Cerebral Cortex
Cerebral Cortex & Hemispheres Location Outermost part of the brain. Organized into two halves: Left & Right Cerebral Hemispheres Analyzes all sensory information. Control of voluntary movements & other complex actions (higher order thought). Function Associated Parts Organized into lobes & and various cortical regions.
Corpus Collosum Location Bundle of nerves which connects the cerebral hemispheres and the various lobes. Function Allows the brain to operate as one unified whole.
Gyri & Sulci Location Gyri: Make up the ridges of the cortex. Sulci: Make up the fissures (valleys) of the cortex. Function Help identify the major cortex areas.
Anatomical Areas: Lobes
Frontal Lobe Location Top front part of the brain, behind the eyes. Function Creativity, problem solving, attention, initiative, physical reaction, sense of smell & libido.
Parietal Lobe Location Top to the back of the brain. Function Touch, sensory & spatial comprehension, language & reading functions. Functions
Temporal Lobe Location Behind the temple region. Function Auditory & visual memory, fear, sense of identity, some hearing & speech.
Occipital Lobe Location Back of the brain. Function Vision & some reading.
Functional Areas: Cortices & Areas
Sensory Cortex Visual Cortex Auditory Cortex Somatosensory Cortex Receives visual information Receives auditory information Receives touch, pain, and temperature information Monitors Proprioception Made up of cells in the Occipital Lobe Made up of cells in the Temporal Lobe. Made up of cells in the Parietal Lobe.
Somatosensory Cortex Allows people to interpret a wide range of sensations. Network of specialized cells on the skin fire & travel to the thalamus. The thalamus relays the info to the somatosensory cortex. Each area of the cortex corresponds with the specialized cells in the skin.
Sensory Homunculus The link between skin locations & locations in the som. cortex have been demonstrated during brain surgery. Research shows particular sensory inputs can be changed by experience.
The Motor Cortex Located in the Frontal Lobe. Create voluntary movements in specific parts of the body. Specialized neurons control movement of the hand, foot, etc. Translates locations in space relative to your body & which muscles to activate at what force.
Motor Homunculus
The Association Cortex Multiple A.C. s throughout the brain. Perform complex cognitive tasks (such as associating words w/ images). Broca s Area: Located in the F.L. Controls the muscles which produce speech. Wernicke s Area: Located in the T.L. Involved in the interpretation of speech & the ability to understand word meaning.
Association Cortex Damage Broca s Aphasia Mental organization of speech suffers. Results in difficulty speaking. Speech is often grammatically incorrect. Words come slowly (perhaps stuttering) Wernicke s Aphasia Disrupts ability to understand the meaning of words. Also disrupts the ability for the person to speak understandably (word organization, context, etc.)