The Central Nervous system SBI4U AP

Agenda Prep for Thursday’s Lab (3 Parts of the Brain – forebrain, midbrain, hindbrain) Dissection Video Individual/group work – looking up terms Read pp. 1090-1093 Chemical Synapse Activity

Components of the nervous system Adapted from: Biology: A Human Perspective. Brock University: Pearson

The 3 Neurons of the nervous system Functional Unit of the Nervous System – cells that are specialized for communication Sensory Neurons: Located in the PNS. Provide input to CNS (Afferent Pathway) Interneurons: Located in the CNS. Integrate input from PNS and influence the functioning of other neurons Motor Neurons: Carry CNS output to all tissues and organs in body (Efferent Pathway)

Cerebral Spinal fluid (Csf) p. 1082 Filtered from Arterial Blood – Supplies CNS with nutrition and removes waste Cushions Brain and Spinal Cord Located in the central canal of spinal cord and ventricles of brain Ependymal Cells – line the ventricles of the brain and the spinal canal. Cilia promote circulation of CSF Grey Matter: neuron cell bodies, dendrites and unmyelinated axons White Matter: Myelinated axons

Protecting the Brain Housed within the skull and surrounded by CSF Brain is surrounded by Meninges (Dura Mater, Arachnoid, Pia Mater) Hydrocephalus: increased accumulation of CSF can lead to pressure on the brain

Adult Brain Forebrain Midbrain Hindbrain

Forebrain Consists of: Cerebrum Hypothalamus Thalamus

1. Cerebrum (aka cortex) Largest part of human brain – Divided into Two Hemispheres that are connected by the Corpus Callosum (myelinated axon fibers) Coordinates language Controls decision making Produces conscious thought Cerebrum is wrinkled to allow increased grey matter

Brain Lateralization Left Hemisphere: Broca’s (frontal lobe – trouble speaking fluently) and Wernicke’s area (temporal lobe – trouble comprehending speech) reside in left cortical hemisphere (Language, Math and Logic) Right Hemisphere: spatial relation, nonverbal thinking, face and pattern recognition https://www.youtube.com/watch?v=ZMLzP1VCANo

Phineas Gage p. 1092

The 4 Lobes of the Cerebrum

Look Up Primary Motor and Primary Sensory Cortex Broca’s and Wernicke’s area Try this website: http://thebrain.mcgill.ca/index.php

2. Hypothalamus Located at the Base of the Forebrain Links nervous system to endocrine system via interactions with the pituitary gland Water and solute balance, temperature control, hunger center and thirst center Suprachiasmatic nucleus (SCN)

3. Thalamus Located superior (above) hypothalamus Receiving, processing and transfer center Example – pain, pressure and temperature changes - cannot identify where it originates from until information is relayed to cerebrum

Midbrain Coordinates movements of head related to vision and hearing (e.g. turning toward sudden sound or flashing light)

HindBrain Posterior (behind) to midbrain. Joins with spinal cord. Oldest, most primitive brain division One of the most similar among animals Consists of: Medulla Oblongata Pons Cerebellum Collectively known as the “brain stem”

Medulla Oblongata Connects to spinal cord Vital automatic functions of internal organs Respiratory center(Oxygen and carbon dioxide levels) and Cardiovascular center (heart rate and blood pressure) Reflexes such as coughing and sneezing All signals passing from brain stem to higher areas of the brain pass through medulla (Look up crossover)

Pons Latin for “bridge” Just superior (above) and partially surrounding medulla Connects cerebellum to higher brain centers Aids medulla in regulating respiration

Cerebellum Posterior to medulla oblongata 2 hemispheres with highly folded surface like cerebrum Coordinates basic body movements that are below the level of conscious control (e.g. ensures antagonistic muscles do not contract at the same time) Coordinates skilled movements (e.g. shifting a car) Receives signals from joint and muscle receptors; balance and position receptors

Look Up Lateral and Longitudinal Fissures Central Sulcus

Structure of a neuron

Neuron Structure Cell Body: nucleus and DNA, mitochondria and other organelles Dendrites: extensions from cell body. Receive information from receptors or other neurons Axon: specialized to conduct electrical impulses. Originate from dendrite in sensory neuron and axon hillock in interneurons and motor neurons. Axons branch into slender extensions known as Axon Terminals. Each axon terminal has a rounded tip known as an axon bulb

Glia in the vertebrate Nervous system (Fig 49.3, p. 1081)

Glia con’t Ependymal Cells – line the ventricles of the brain. Cilia promote circulation of CSF Astrocytes – Located in CNS. Facilitate information transfer at Synapses. Regulate nutrition (oxygen and glucose) for neurons by regulating nearby blood vessels. In addition, astrocytes regulate extracellular concentrations of ions and neurotransmitters Oligodendrocytes: myelinate axons in CNS Microglia: immune cells in CNS Schwann cells: myelinate axons in PNS

Synapse: How Neurons “Talk” to Each Other

Readings Read 49.3, pp. 1090 – 1093 Read 48.1 and 48.2, pp. 1062 –1066