CNS Notes Parts of the Brain

CNS = BRAIN + SPINAL CORD The spinal cord connects the CNS to the PNS via nerves that travel through a canal inside the backbone Sensory neurons carry impulses from the sensory receptors in the periphery to the brain Motor neurons carry impulses from the brain to the effectors (muscles, glands, organs) The spinal cord is also the primary reflex centre – allowing the body to react quickly to potentially dangerous situations

Spinal cord Contains white matter and grey matter White mattermyelinated nerve fibres from sensory and motor neurons Grey matternonmyelinated interneurons

Brain protection Cranium = skull Cranium and mandible of documented 17 year old. Manner of death was two gunshot wounds, and cranium shows classic entrance and exit wounds. From Maxwell Museum, Albuquerque, NM.

Brain protection – con’t Meninges 3 membranes surrounding the brain Make up the blood-brain barrier – allow a separation of blood in the brain – although some substances do cross (ie alcohol, caffeine, nicotine, heroin, other lipid-soluble substances)

Brain injury Why do we wear helmets?

Brain Forebrain Midbrain Hindbrain Primary cortical areas-receive signals from receptors on the body’s periphery Association areas-coordinate and process sensory input from different receptors

Forebrain Cerebrum Thalamus Hypothalamus Olfactory bulbs Largest, most developed part of the brain Thalamus Coordinates and interprets sensory information and directs to appropriate part of cerebrum Hypothalamus Coordinates nerve and hormone functions; directly connected to pituitary gland; maintains internal equilibrium Olfactory bulbs One in each hemisphere; process information about smell

Hypothalamus Influences HR, BP, resp. rate, Autonomic regulatory center Influences HR, BP, resp. rate, GI motility, pupillary diameter. Emotional response Involved in fear, loathing, pleasure Drive center: sex, hunger Regulation of body temperature Regulation of food intake Contains a satiety center Regulation of water balance and thirst Regulation of sleep/wake cycles Hormonal control Releases hormones to the pituitary gland

Pituitary gland A gland that lies just beneath the hypothalamus Divided into anterior and posterior pituitary Responsible for the production of many different hormones

Cerebrum Divided into two hemispheres; left and right Right side: visual patterns and spatial awareness Left side: verbal skills Further subdivided into 4 lobes (frontal, temporal, occipital, parietal) Cerebral cortex: outer layer of the cerebral hemispheres Grey matter Deep folds increase surface area Corpus Callosum Nerve tract that joins the two cerebral hemispheres; allows communication between the two sides

Scientists believe that epilepsy is caused by an overload of neurological electrical activity – so the corpus callosum is sometimes cut in an epilepsy patient to prevent the seizures from spreading from one hemisphere to the other.

Lobes of the Cerebrum Frontal Temporal Parietal Occipital Motor areas control voluntary muscles Temporal Sensory areas associated with vision and hearing Parietal Sensory areas associated with touch and temperature Association areas linked with emotions and interpreting speech Occipital Sensory areas associated with vision Association areas interpret visual information

Sensory Areas Found in the parietal, occipital, and temporal lobes. Parietal lobe Temporal lobe Occipital lobe

Motor Area Frontal Lobe Controls fine motor movements – but innervation is not equal – some parts of the body have a larger proportion of the motor area devoted to them than others Contains large neurons which synapse on skeletal muscles Allow for voluntary motor control

Midbrain 4 spheres of grey matter Relay centre for some eye and ear reflexes

Hindbrain Cerebellum Medulla oblongata Pons Largest section of hindbrain Controls limb movements, balance and muscle tone Medulla oblongata Connects the peripheral and central nervous systems Joins spinal cord to cerebellum Responsible for involuntary muscle action Pons Part of brain that bridges the cerebellum and medulla, acts as a relay station

Cerebellum Has 2 primary functions: 2nd largest region of the brain. 10% of the brain by volume, but it contains 50% of its neurons Has 2 primary functions: Adjusting the postural muscles of the body Coordinates rapid, automatic adjustments, that maintain balance and equilibrium Programming and fine-tuning movements controlled at the subconscious and conscious levels Compares motor commands with sensory info from muscles and joints and performs any adjustments to make the movement smooth

Your Turn Read pg 430 and discuss questions 1-3 with a friend Complete questions 1-4 & 8 on pg. 432